Global characterization of the Holocene Thermal Maximum
Renssen, H.; Seppä, H.; Crosta, X.; Goosse, H.; Roche, D.M.V.A.P.
2012-01-01
We analyze the global variations in the timing and magnitude of the Holocene Thermal Maximum (HTM) and their dependence on various forcings in transient simulations covering the last 9000 years (9 ka), performed with a global atmosphere-ocean-vegetation model. In these experiments, we consider the i
Regulation of Unperturbed DNA Replication by Ubiquitylation
Sara Priego Moreno
2015-06-01
Full Text Available Posttranslational modification of proteins by means of attachment of a small globular protein ubiquitin (i.e., ubiquitylation represents one of the most abundant and versatile mechanisms of protein regulation employed by eukaryotic cells. Ubiquitylation influences almost every cellular process and its key role in coordination of the DNA damage response is well established. In this review we focus, however, on the ways ubiquitylation controls the process of unperturbed DNA replication. We summarise the accumulated knowledge showing the leading role of ubiquitin driven protein degradation in setting up conditions favourable for replication origin licensing and S-phase entry. Importantly, we also present the emerging major role of ubiquitylation in coordination of the active DNA replication process: preventing re-replication, regulating the progression of DNA replication forks, chromatin re-establishment and disassembly of the replisome at the termination of replication forks.
Continental warming preceding the Palaeocene-Eocene thermal maximum.
Secord, Ross; Gingerich, Philip D; Lohmann, Kyger C; Macleod, Kenneth G
2010-10-21
Marine and continental records show an abrupt negative shift in carbon isotope values at ∼55.8 Myr ago. This carbon isotope excursion (CIE) is consistent with the release of a massive amount of isotopically light carbon into the atmosphere and was associated with a dramatic rise in global temperatures termed the Palaeocene-Eocene thermal maximum (PETM). Greenhouse gases released during the CIE, probably including methane, have often been considered the main cause of PETM warming. However, some evidence from the marine record suggests that warming directly preceded the CIE, raising the possibility that the CIE and PETM may have been linked to earlier warming with different origins. Yet pre-CIE warming is still uncertain. Disentangling the sequence of events before and during the CIE and PETM is important for understanding the causes of, and Earth system responses to, abrupt climate change. Here we show that continental warming of about 5 °C preceded the CIE in the Bighorn Basin, Wyoming. Our evidence, based on oxygen isotopes in mammal teeth (which reflect temperature-sensitive fractionation processes) and other proxies, reveals a marked temperature increase directly below the CIE, and again in the CIE. Pre-CIE warming is also supported by a negative amplification of δ(13)C values in soil carbonates below the CIE. Our results suggest that at least two sources of warming-the earlier of which is unlikely to have been methane-contributed to the PETM.
Coupling diffusion and maximum entropy models to estimate thermal inertia
Thermal inertia is a physical property of soil at the land surface related to water content. We have developed a method for estimating soil thermal inertia using two daily measurements of surface temperature, to capture the diurnal range, and diurnal time series of net radiation and specific humidi...
Haseli, Y
2016-05-01
The objective of this study is to investigate the thermal efficiency and power production of typical models of endoreversible heat engines at the regime of minimum entropy generation rate. The study considers the Curzon-Ahlborn engine, the Novikov's engine, and the Carnot vapor cycle. The operational regimes at maximum thermal efficiency, maximum power output and minimum entropy production rate are compared for each of these engines. The results reveal that in an endoreversible heat engine, a reduction in entropy production corresponds to an increase in thermal efficiency. The three criteria of minimum entropy production, the maximum thermal efficiency, and the maximum power may become equivalent at the condition of fixed heat input.
Thermal properties for the thermal-hydraulics analyses of the BR2 maximum nominal heat flux.
Dionne, B.; Kim, Y. S.; Hofman, G. L. (Nuclear Engineering Division)
2011-05-23
This memo describes the assumptions and references used in determining the thermal properties for the various materials used in the BR2 HEU (93% enriched in {sup 235}U) to LEU (19.75% enriched in {sup 235}U) conversion feasibility analysis. More specifically, this memo focuses on the materials contained within the pressure vessel (PV), i.e., the materials that are most relevant to the study of impact of the change of fuel from HEU to LEU. This section is regrouping all of the thermal property tables. Section 2 provides a summary of the thermal properties in form of tables while the following sections present the justification of these values. Section 3 presents a brief background on the approach used to evaluate the thermal properties of the dispersion fuel meat and specific heat capacity. Sections 4 to 7 discuss the material properties for the following materials: (i) aluminum, (ii) dispersion fuel meat (UAlx-Al and U-7Mo-Al), (iii) beryllium, and (iv) stainless steel. Section 8 discusses the impact of irradiation on material properties. Section 9 summarizes the material properties for typical operating temperatures. Appendix A elaborates on how to calculate dispersed phase's volume fraction. Appendix B shows the evolution of the BR2 maximum heat flux with burnup.
Larsen, Ulrik; Pierobon, Leonardo; Wronski, Jorrit;
2014-01-01
to power. In this study we propose four linear regression models to predict the maximum obtainable thermal efficiency for simple and recuperated ORCs. A previously derived methodology is able to determine the maximum thermal efficiency among many combinations of fluids and processes, given the boundary...
Efficiency at maximum power of thermally coupled heat engines.
Apertet, Y; Ouerdane, H; Goupil, C; Lecoeur, Ph
2012-04-01
We study the efficiency at maximum power of two coupled heat engines, using thermoelectric generators (TEGs) as engines. Assuming that the heat and electric charge fluxes in the TEGs are strongly coupled, we simulate numerically the dependence of the behavior of the global system on the electrical load resistance of each generator in order to obtain the working condition that permits maximization of the output power. It turns out that this condition is not unique. We derive a simple analytic expression giving the relation between the electrical load resistance of each generator permitting output power maximization. We then focus on the efficiency at maximum power (EMP) of the whole system to demonstrate that the Curzon-Ahlborn efficiency may not always be recovered: The EMP varies with the specific working conditions of each generator but remains in the range predicted by irreversible thermodynamics theory. We discuss our results in light of nonideal Carnot engine behavior.
Nutrition modifies critical thermal maximum of a dominant canopy ant.
Bujan, Jelena; Kaspari, Michael
2017-10-01
While adaptive responses to climate gradients are increasingly documented, little is known about how individuals alter their upper thermal tolerances. Long-term increases in dietary carbohydrates can elevate upper thermal tolerances in insects. We explored how the nutritional state of a Neotropical canopy ant governs its CTmax - the temperature at which individuals lose muscle control. We predicted that Azteca chartifex workers recently fed a carbohydrate-rich diet, such as honeydew and extrafloral nectar, would use that energy to increase their CTmax. Moreover, if a carbohydrate-rich diet increases CTmax, then we predicted that ants from colonies with high CTmaxs feed at a lower trophic level, and thus have a higher carbon:nitrogen ratio. We used A. chartifex colonies from a long-term fertilization experiment where phosphorus addition increased A. chartifex foraging activity with respect to controls. As foraging activity can be governed by resource availability, we first measured CTmax of field collected colonies. In freshly collected field colonies, CTmax was 2°C higher in control plots. This difference disappeared when ants were provided with only water for 10h. Ants were then provided with a 10% sucrose solution ad lib which increased CTmax by 5°C. We thus support the hypothesis that enhanced carbohydrate nutrition enables higher thermal tolerance, but this does not appear to be linked to colony trophic status, higher carbon:nitrogen ratios, or higher total body phosphorus. This short-term thermal plasticity linked to carbohydrate nutrition demonstrates the importance of ant diet in shaping their physiological traits. It is especially relevant to ant species that maintain high abundance by feeding on plant exudates. In a rapidly warming world, carbohydrate availability and use may represent a new element for predicting population and community responses of herbivorous insects. Copyright © 2017. Published by Elsevier Ltd.
Y. Haseli
2016-05-01
Full Text Available The objective of this study is to investigate the thermal efficiency and power production of typical models of endoreversible heat engines at the regime of minimum entropy generation rate. The study considers the Curzon-Ahlborn engine, the Novikov’s engine, and the Carnot vapor cycle. The operational regimes at maximum thermal efficiency, maximum power output and minimum entropy production rate are compared for each of these engines. The results reveal that in an endoreversible heat engine, a reduction in entropy production corresponds to an increase in thermal efficiency. The three criteria of minimum entropy production, the maximum thermal efficiency, and the maximum power may become equivalent at the condition of fixed heat input.
Unperturbed Schelling Segregation in Two or Three Dimensions
Barmpalias, George; Elwes, Richard; Lewis-Pye, Andrew
2016-09-01
Schelling's models of segregation, first described in 1969 (Am Econ Rev 59:488-493, 1969) are among the best known models of self-organising behaviour. Their original purpose was to identify mechanisms of urban racial segregation. But his models form part of a family which arises in statistical mechanics, neural networks, social science, and beyond, where populations of agents interact on networks. Despite extensive study, unperturbed Schelling models have largely resisted rigorous analysis, prior results generally focusing on variants in which noise is introduced into the dynamics, the resulting system being amenable to standard techniques from statistical mechanics or stochastic evolutionary game theory (Young in Individual strategy and social structure: an evolutionary theory of institutions, Princeton University Press, Princeton, 1998). A series of recent papers (Brandt et al. in: Proceedings of the 44th annual ACM symposium on theory of computing (STOC 2012), 2012); Barmpalias et al. in: 55th annual IEEE symposium on foundations of computer science, Philadelphia, 2014, J Stat Phys 158:806-852, 2015), has seen the first rigorous analyses of 1-dimensional unperturbed Schelling models, in an asymptotic framework largely unknown in statistical mechanics. Here we provide the first such analysis of 2- and 3-dimensional unperturbed models, establishing most of the phase diagram, and answering a challenge from Brandt et al. in: Proceedings of the 44th annual ACM symposium on theory of computing (STOC 2012), 2012).
Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling
Yan, H; Guo, H.
2012-01-01
We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson eng...
Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling.
Yan, H; Guo, Hao
2012-01-01
We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson engines. While in the short contact time limit, which corresponds to the Carnot cycle, the same efficiency bounds as that from Esposito et al. [Phys. Rev. Lett. 105, 150603 (2010)] are derived. In both cases, the thermal efficiency decreases as the ratio between the heat capacities of the working medium during heating and cooling stages increases. This might provide instructions for designing real engines.
Efficiency and its bounds for thermal engines at maximum power using Newton's law of cooling
Yan, H.; Guo, Hao
2012-01-01
We study a thermal engine model for which Newton's cooling law is obeyed during heat transfer processes. The thermal efficiency and its bounds at maximum output power are derived and discussed. This model, though quite simple, can be applied not only to Carnot engines but also to four other types of engines. For the long thermal contact time limit, new bounds, tighter than what were known before, are obtained. In this case, this model can simulate Otto, Joule-Brayton, Diesel, and Atkinson engines. While in the short contact time limit, which corresponds to the Carnot cycle, the same efficiency bounds as that from Esposito [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.105.150603 105, 150603 (2010)] are derived. In both cases, the thermal efficiency decreases as the ratio between the heat capacities of the working medium during heating and cooling stages increases. This might provide instructions for designing real engines.
Latella Ivan
2014-01-01
Full Text Available We analyse the process of conversion of near-field thermal radiation into usable work by considering the radiation emitted between two planar sources supporting surface phonon-polaritons. The maximum work flux that can be extracted from the radiation is obtained taking into account that the spectral flux of modes is mainly dominated by these surface modes. The thermodynamic efficiencies are discussed and an upper bound for the first law efficiency is obtained for this process.
Sharply increased insect herbivory during the Paleocene–Eocene Thermal Maximum
Currano, Ellen D.; Wilf, Peter; Wing, Scott L.; Labandeira, Conrad C.; Lovelock, Elizabeth C.; Royer, Dana L.
2008-01-01
The Paleocene–Eocene Thermal Maximum (PETM, 55.8 Ma), an abrupt global warming event linked to a transient increase in pCO2, was comparable in rate and magnitude to modern anthropogenic climate change. Here we use plant fossils from the Bighorn Basin of Wyoming to document the combined effects of temperature and pCO2 on insect herbivory. We examined 5,062 fossil leaves from five sites positioned before, during, and after the PETM (59–55.2 Ma). The amount and diversity of insect damage on angiosperm leaves, as well as the relative abundance of specialized damage, correlate with rising and falling temperature. All reach distinct maxima during the PETM, and every PETM plant species is extensively damaged and colonized by specialized herbivores. Our study suggests that increased insect herbivory is likely to be a net long-term effect of anthropogenic pCO2 increase and warming temperatures. PMID:18268338
The Paleocene - Eocene Thermal Maximum: Temperature and Ecology in the Tropics
Frieling, J.; Gebhardt, H.; Adekeye, O. A.; Akande, S. O.; Reichart, G. J.; Middelburg, J. J. B. M.; Schouten, S.; Huber, M.; Sluijs, A.
2014-12-01
Various records across the Paleocene - Eocene Thermal Maximum (PETM) have established approximately 5 °C of additional surface and deep ocean warming, superimposed on the already warm latest Paleocene. The PETM is further characterized by a global negative stable carbon isotope excursion (CIE), poleward migration of thermophilic biota, ocean acidification, increased weathering, photic zone euxinia and intensified hydrological cycle. Reconstructed temperatures for the PETM in mid and high-latitudes regularly exceed modern open marine tropical temperatures. Constraints on absolute tropical temperatures are, however, limited. We studied the PETM in a sediment section from the Nigerian sector of the Dahomey Basin, deposited on the shelf near the equator. We estimate sea surface temperatures by paired analyses of TEX86, and Mg/Ca and δ18O of foraminifera from the Shagamu Quarry. These show Palaeocene temperatures of ~33 °C and SSTs rose by 4 °C during the PETM based on TEX86. During the PETM, intermittent photic zone euxinia developed based on the presence of the biomarker isorenieratane. Interestingly, during peak warmth, dinoflagellate cyst abundances and diversity are remarkably low. From our new data and evidence from modern dinoflagellate experiments, we conclude that thermal stress was the main driver for this observation. We derive that endothermal and most ectothermal nektonic and planktonic marine eukaryotic organisms could not have lived in the surface waters in this part of the tropics during the PETM.
Jenö Nagy
2013-07-01
Full Text Available The study deals with environmental changes during the Paleocene–Eocene Thermal Maximum (PETM and its background conditions in Spitsbergen through analysis of benthic foraminiferal assemblages (FA in a section drilled in the Paleogene Central Basin. The impact of this extreme global warming occurs here in prodelta shelf mudstones composing the lower part of the Gilsonryggen Member (Frysjaodden Formation. The start of the PETM perturbation is marked by a faunal turnover, in which the medium-diversity circumpolar Reticulophragmium assemblage was replaced by a low-diversity Trochammina fauna. During the hyperthermal period, benthic foraminiferal diversity decreased severely, while the dominance of small-sized taxa with epifaunal morphology strongly increased. This low-diversity fauna occurs in sediments with a reduced thorium/uranium ratio (proxy for oxygenation and kaolinite enrichment (proxy for high humidity. The faunal changes were thus caused by the combined effects of hypoxic and hyposaline conditions in a stratified water column, due to extreme warming with its accompanying intensified hydrologic cycle. The PETM acme coincides with the maximum flooding surface (MFS of the Gilsonryggen depositional sequence, composed of the Gilsonryggen Member and the overlying Battfjellet and Aspelintoppen formations. The transgressive phase of the sequence was initiated by local tectonics, while the eustatic sea-level rise of the PETM was superimposed on this transgression.To access the supplementary material for this article, please see supplementary files under Article Tools online.
Elhussain, O. A.; Abdel-Magid, T. I. M.
2016-08-01
Mono-Crystalline solar cell module is experimentally conducted in Khartoum, Sudan to study the difference between maximum empirical value of peak Watt and maximum value of thermal power produced in field under highly sufficient solar conditions. Field measurements are recorded for incident solar radiation, produced voltage, current and temperature at several time intervals during sun shine period. The thermal power system has been calculated using fundamental principles of heat transfer. The study shows that solar power for considered module could not attain the empirical peak power irrespective to maximum value of direct incident solar radiation and maximum temperature gained. A loss of about 6% of power can be considered as the difference between field measurements and the manufacturer's indicated empirical value. Solar cell exhibits 94% efficiency in comparison with manufacturer's provided data, and is 3'% more efficient in thermal energy production than in electrical power extraction for hot-dry climate conditions.
Productivity response of calcareous nannoplankton to Eocene Thermal Maximum 2 (ETM2)
Dedert, M.; Stoll, H. M.; Kroon, D.; Shimizu, N.; Kanamaru, K.; Ziveri, P.
2012-05-01
The Early Eocene Thermal Maximum 2 (ETM2) at ~53.7 Ma is one of multiple hyperthermal events that followed the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma). The negative carbon excursion and deep ocean carbonate dissolution which occurred during the event imply that a substantial amount (103 Gt) of carbon (C) was added to the ocean-atmosphere system, consequently increasing atmospheric CO2(pCO2). This makes the event relevant to the current scenario of anthropogenic CO2 additions and global change. Resulting changes in ocean stratification and pH, as well as changes in exogenic cycles which supply nutrients to the ocean, may have affected the productivity of marine phytoplankton, especially calcifying phytoplankton. Changes in productivity, in turn, may affect the rate of sequestration of excess CO2 in the deep ocean and sediments. In order to reconstruct the productivity response by calcareous nannoplankton to ETM2 in the South Atlantic (Site 1265) and North Pacific (Site 1209), we employ the coccolith Sr/Ca productivity proxy with analysis of well-preserved picked monogeneric populations by ion probe supplemented by analysis of various size fractions of nannofossil sediments by ICP-AES. The former technique of measuring Sr/Ca in selected nannofossil populations using the ion probe circumvents possible contamination with secondary calcite. Avoiding such contamination is important for an accurate interpretation of the nannoplankton productivity record, since diagenetic processes can bias the productivity signal, as we demonstrate for Sr/Ca measurements in the fine (productivity during ETM2. This high productivity phase is probably the result of enhanced nutrient supply either from land or from upwelling. The ion probe results show that calcareous nannoplankton productivity was not reduced by environmental conditions accompanying ETM2 at Site 1265, but imply an overall sustained productivity and potentially a small productivity increase during the extreme
Productivity response of calcareous nannoplankton to Eocene Thermal Maximum 2 (ETM2
M. Dedert
2012-05-01
Full Text Available The Early Eocene Thermal Maximum 2 (ETM2 at ~53.7 Ma is one of multiple hyperthermal events that followed the Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma. The negative carbon excursion and deep ocean carbonate dissolution which occurred during the event imply that a substantial amount (10^{3} Gt of carbon (C was added to the ocean-atmosphere system, consequently increasing atmospheric CO_{2}(pCO_{2}. This makes the event relevant to the current scenario of anthropogenic CO_{2} additions and global change. Resulting changes in ocean stratification and pH, as well as changes in exogenic cycles which supply nutrients to the ocean, may have affected the productivity of marine phytoplankton, especially calcifying phytoplankton. Changes in productivity, in turn, may affect the rate of sequestration of excess CO_{2} in the deep ocean and sediments. In order to reconstruct the productivity response by calcareous nannoplankton to ETM2 in the South Atlantic (Site 1265 and North Pacific (Site 1209, we employ the coccolith Sr/Ca productivity proxy with analysis of well-preserved picked monogeneric populations by ion probe supplemented by analysis of various size fractions of nannofossil sediments by ICP-AES. The former technique of measuring Sr/Ca in selected nannofossil populations using the ion probe circumvents possible contamination with secondary calcite. Avoiding such contamination is important for an accurate interpretation of the nannoplankton productivity record, since diagenetic processes can bias the productivity signal, as we demonstrate for Sr/Ca measurements in the fine (<20 μm and other size fractions obtained from bulk sediments from Site 1265. At this site, the paleoproductivity signal as reconstructed from the Sr/Ca appears to be governed by cyclic changes, possibly orbital forcing, resulting in a 20–30% variability in Sr/Ca in dominant genera as obtained by ion probe. The ~13 to 21
Productivity feedback did not terminate the Paleocene-Eocene Thermal Maximum (PETM
A. Torfstein
2009-10-01
Full Text Available The Paleocene-Eocene Thermal Maximum (PETM occurred approximately 55 million years ago, and is one of the most dramatic abrupt global warming events in the geological record. This warming was triggered by the sudden release of thousands of gigatons of carbon into the atmosphere and is widely perceived to be the best analogue for current anthropogenic climate change. Yet, the mechanism of recovery from this event remains controversial. A massive increase in the intensity of the marine biological pump (''productivity feedback'' has been suggested to cause a drawdown of atmospheric CO_{2} and subsequent carbon sequestration in the ocean. A re-evaluation of the ''productivity feedback hypothesis'', based on biogenic barium mass accumulation rates (Ba-MARs for a site in the Southern Ocean, finds that any increase in export production lagged the initial carbon release by at least ~70 000 years. This implies that export production did not rapidly remove excess carbon from the atmosphere, and renders the most likely mechanism for carbon removal to be silicate weathering, at much slower rates than previously assumed.
Constraints on ocean circulation at the Paleocene–Eocene Thermal Maximum from neodymium isotopes
A. N. Abbott
2015-06-01
Full Text Available Global warming during the Paleocene Eocene Thermal Maximum (PETM ~55 million years ago (Ma coincided with a massive release of carbon to the ocean–atmosphere system, as indicated by carbon isotopic data. Previous studies have argued for a role for changing ocean circulation, possibly as a trigger or response to climatic changes. We use neodymium (Nd isotopic data to reconstruct short high-resolution records of deep-water circulation across the PETM. These records are derived by reductively leaching sediments from seven globally distributed sites and comparing data with published data from fossil fish debris to reconstruct past deep ocean circulation across the PETM. The Nd data for the leachates are interpreted to be consistent with previous studies that have used fish teeth and benthic foraminiferal δ13C to constrain regions of convection. There is some evidence from combining Nd isotope and δ13C records that the three major ocean basins may not have had substantial exchanges of deep waters. If the isotopic data are interpreted within this framework, then the observed pattern may be explained if the strength of overturning in each basin varied distinctly over the PETM, resulting in differences in deep-water aging gradients between basins. Results are consistent with published interpretations from proxy data and model simulations that suggest modulation of overturning circulation had an important role for global recovery of the ocean–atmosphere system after the PETM.
Very large release of mostly volcanic carbon during the Palaeocene-Eocene Thermal Maximum
Gutjahr, Marcus; Ridgwell, Andy; Sexton, Philip F.; Anagnostou, Eleni; Pearson, Paul N.; Pälike, Heiko; Norris, Richard D.; Thomas, Ellen; Foster, Gavin L.
2017-08-01
The Palaeocene-Eocene Thermal Maximum (PETM) was a global warming event that occurred about 56 million years ago, and is commonly thought to have been driven primarily by the destabilization of carbon from surface sedimentary reservoirs such as methane hydrates. However, it remains controversial whether such reservoirs were indeed the source of the carbon that drove the warming. Resolving this issue is key to understanding the proximal cause of the warming, and to quantifying the roles of triggers versus feedbacks. Here we present boron isotope data—a proxy for seawater pH—that show that the ocean surface pH was persistently low during the PETM. We combine our pH data with a paired carbon isotope record in an Earth system model in order to reconstruct the unfolding carbon-cycle dynamics during the event. We find strong evidence for a much larger (more than 10,000 petagrams)—and, on average, isotopically heavier—carbon source than considered previously. This leads us to identify volcanism associated with the North Atlantic Igneous Province, rather than carbon from a surface reservoir, as the main driver of the PETM. This finding implies that climate-driven amplification of organic carbon feedbacks probably played only a minor part in driving the event. However, we find that enhanced burial of organic matter seems to have been important in eventually sequestering the released carbon and accelerating the recovery of the Earth system.
Increased precipitation and weathering across the Paleocene-Eocene Thermal Maximum in central China
Chen, Zuoling; Ding, Zhongli; Yang, Shiling; Zhang, Chunxia; Wang, Xu
2016-06-01
Global warming during the Paleocene-Eocene Thermal Maximum (PETM) ˜55.5 million years ago (Ma) was associated with a massive release of carbon to the ocean-atmosphere system, as evidenced by a prominent negative carbon isotope excursion (CIE) and widespread dissolution of marine carbonates. The paleohydrologic response to the PETM warming has been studied worldwide; however, relevant records of environmental perturbation in Asia are lacking so far. Here we extend the record of this event in central China, a subtropical paleosetting, through geochemical and mineralogical analyses of lacustrine sediments. Geochemical indicators of authigenic carbonates—including molar Mg/Ca and Sr/Ca ratios—suggest an overall increased precipitation across the PETM, compatible with the disappearance of authigenic dolomite and the appearance of kaolinite in the strata. The relatively humid conditions persisted long after the carbon-cycle perturbation had stopped, implying that the transient hyper-greenhouse warming might have forced the regional climate system into a new climate state that was not easily reversed. Additionally, a gradual increase in chemical index of alteration (CIA) and the appearance of kaolinite are associated with the PETM, indicating an intensified silicate weathering and pedogenesis in the watershed in response to warmer and more humid climate. Our results corroborate the theory that an accelerated continental chemical weathering served as a negative feedback to sequester carbon and lower the atmospheric greenhouse-gas levels during the PETM.
A Smoking Gun for Methane Hydrate Release During the Paleocene-Eocene Thermal Maximum
Frieling, J.; Peterse, F.; Lunt, D. J.; Bohaty, S. M.; S Sinninghe Damsté, J.; Reichart, G. J.; Sluijs, A.
2016-12-01
The Paleocene-Eocene Thermal Maximum (PETM; 56 Ma) was a period of rapid 4-5ºC global warming and a global negative carbon isotope excursion (CIE) of 3-4.5‰, signaling the input of at least 1500 Gt of δ13C-depleted carbon into the ocean-atmosphere system. Methane from submarine hydrates has long been proposed as a carbon source, but direct and indirect evidence is lacking. We generated a new high-resolution TEX86 and δ13C record from Ocean Drilling Program Site 959 in the eastern tropical Atlantic and find that initial warming preceded the PETM CIE by 10 kyr. Moreover, time-shifted cross-correlations on these new and published temperature-δ13C data imply that substantial (2-3 °C) warming lead 13C-depleted carbon injection by an average of 2-3 kyr globally. Finally, a data compilation shows that global burial fluxes of biogenic Ba approximately doubled across all depths of the ocean studied, which on PETM time scales can only be explained by significant Ba addition to the oceans. Submarine hydrates are Ba-rich and require warming to dissociate. The simplest explanation for the temperature lead and Ba addition to the ocean is that methane hydrate dissociated as a response to initial warming and acted as a positive carbon cycle feedback during the PETM.
Cui, Y.; Kump, L.; Diefendorf, A. F.; Freeman, K. H.
2011-12-01
The Paleocene-Eocene Thermal Maximum (PETM; ca. 55.9 Ma) was an interval of geologically abrupt global warming lasting ~200 ka. It has been proposed as an ancient analogue for future climate response to CO2 emission from fossil fuel burning. The onset of this event is fueled by a large release of 13C-depleted carbon into the ocean-atmosphere system. However, there is a large discrepancy in the magnitude of the carbon isotope excursion (CIE) between marine and terrestrial records. Here we present new organic geochemical data and stable carbon isotope records from n-alkanes and pristane extracted from core materials representing the most expanded PETM section yet recovered from a nearshore marine early Cenozoic succession from Spitsbergen. The low hydrogen index and oxygen index indicate that organic matter has been thermally altered, consistent with n-alkanes that do not show a clear odd-over-even predominance as reflected by the low and constant carbon preference index. The δ13C records of long chain n-alkanes from core BH9-05 track the δ13C recorded in total organic carbon, but are ~3% more negative prior to the CIE, ~4.5% more negative during the CIE, and ~4% more negative after the CIE. An orbital age model derived from the same core suggests the CIE from n-alkanes appears more abruptly onset than the bulk organic carbon, indicating possibly climate-induced modification to the observed feature in n-alkanes. In addition, the carbon isotope values of individual long-chain (n-C27 to n-C31) n-alkanes tend to become less negative with increasing chain length resulting in the smallest magnitude CIEs in longer chain lengths (i.e. n-C31) and the largest magnitude CIEs in shorter chain lengths (i.e. n-C27). We are currently considering the effect of plant community and paleoclimate on the observed pattern of CIE in n-alkanes to evaluate carbon cycle perturbations and Arctic hydrology changes during the PETM. One interpretation of these patterns is that there was an
Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum
Denis, Elizabeth H.; Pedentchouk, Nikolai; Schouten, Stefan; Pagani, Mark; Freeman, Katherine H.
2017-06-01
Fire has been an important component of ecosystems on a range of spatial and temporal scales. Fire can affect vegetation distribution, the carbon cycle, and climate. The relationship between climate and fire is complex, in large part because of a key role of vegetation type. Here, we evaluate regional scale fire-climate relationships during a past global warming event, the Paleocene-Eocene Thermal Maximum (PETM), in order to understand how vegetation influenced the links between climate and fire occurrence in the Arctic region. To document concurrent changes in climate, vegetation, and fire occurrence, we evaluated biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes, from the PETM interval at a marine depositional site (IODP site 302, the Lomonosov Ridge) in the Arctic Ocean. Biomarker, fossil, and isotope evidence from site 302 indicates that terrestrial vegetation changed during the PETM. The abundance of the C29n-alkanes, pollen, and the ratio of leaf-wax n-alkanes relative to diterpenoids all indicate that proportional contributions from angiosperm vegetation increased relative to that from gymnosperms. These changes accompanied increased moisture transport to the Arctic and higher temperatures, as recorded by previously published proxy records. We find that PAH abundances were elevated relative to total plant biomarkers throughout the PETM, and suggest that fire occurrence increased relative to plant productivity. The fact that fire frequency or prevalence may have increased during wetter Arctic conditions suggests that changes in fire occurrence were not a simple function of aridity, as is commonly conceived. Instead, we suggest that the climate-driven ecological shift to angiosperm-dominated vegetation was what led to increased fire occurrence. Potential increases in terrestrial plant biomass that arose from warm, wet, and high CO2 conditions were possibly attenuated by biomass burning associated with compositional changes
Grey, J. A.; Bralower, T. J.; Self-Trail, J. M.
2016-12-01
The recovery interval of the Paleocene Eocene Thermal Maximum (PETM) presents an opportunity to examine how organisms adapt to environmental change after a rapid global warming event. Calcareous nannoplankton survived the PETM, but we lack an understanding of how long it took for assemblages to adapt to a changing climate and the millennial-scale changes in their ecology. Here, we present the first high-resolution record of nannoplankton community change during the PETM recovery using a global data set (United States Geological Survey (USGS) Wilson Lake core, USGS Cam-Dor core, Ocean Drilling Program (ODP) Sites 690, 1265, and 1209) to assess millennial-scale assemblage change across space and time. Preliminary multivariate analyses on assemblage changes at Wilson Lake demonstrate that within 20,000 years after the onset, the structure of nannoplankton communities shifts from an assemblage dominated by warm eutrophic specialists to one dominated by eutrophic low salinity specialists. In the late recovery, ubiquitous taxa dominate assemblages, suggesting that the shelf environment became favorable for generalists. The latest part of the recovery is marked by a slight increase in oligotrophic specialists, indicating that the shelf became less eutrophic into the early Eocene. Overall, these analyses suggest that assemblages changed rapidly in response to cooling and changing ocean circulation during the early recovery of the PETM. Future analyses will build on these data by comparing assemblage change from other PETM coastal and open ocean sites. These analyses will help us better understand the spatial and temporal changes of nannoplankton communities on a global scale, lessons that can inform how nannoplankton will respond to future climate change.
A. Sluijs
2011-01-01
Full Text Available A brief (~150 kyr period of widespread global average surface warming marks the transition between the Paleocene and Eocene epochs, ~56 million years ago. This so-called "Paleocene-Eocene thermal maximum" (PETM is associated with the massive injection of ^{13}C-depleted carbon, reflected in a negative carbon isotope excursion (CIE. Biotic responses include a global abundance peak (acme of the subtropical dinoflagellate Apectodinium. Here we identify the PETM in a marine sedimentary sequence deposited on the East Tasman Plateau at Ocean Drilling Program (ODP Site 1172 and show, based on the organic paleothermometer TEX_{86}, that southwest Pacific sea surface temperatures increased from ~26 °C to ~33°C during the PETM. Such temperatures before, during and after the PETM are >10 °C warmer than predicted by paleoclimate model simulations for this latitude. In part, this discrepancy may be explained by potential seasonal biases in the TEX_{86} proxy in polar oceans. Additionally, the data suggest that not only Arctic, but also Antarctic temperatures may be underestimated in simulations of ancient greenhouse climates by current generation fully coupled climate models. An early influx of abundant Apectodinium confirms that environmental change preceded the CIE on a global scale. Organic dinoflagellate cyst assemblages suggest a local decrease in the amount of river run off reaching the core site during the PETM, possibly in concert with eustatic rise. Moreover, the assemblages suggest changes in seasonality of the regional hydrological system and storm activity. Finally, significant variation in dinoflagellate cyst assemblages during the PETM indicates that southwest Pacific climates varied significantly over time scales of 10^{3} – 10^{4} years during this event, a finding comparable to similar studies of PETM successions from the New Jersey Shelf.
Carmichael, Matthew J.; Inglis, Gordon N.; Badger, Marcus P. S.; Naafs, B. David A.; Behrooz, Leila; Remmelzwaal, Serginio; Monteiro, Fanny M.; Rohrssen, Megan; Farnsworth, Alexander; Buss, Heather L.; Dickson, Alexander J.; Valdes, Paul J.; Lunt, Daniel J.; Pancost, Richard D.
2017-10-01
The Paleocene-Eocene Thermal Maximum (PETM) hyperthermal, 56 million years ago (Ma), is the most dramatic example of abrupt Cenozoic global warming. During the PETM surface temperatures increased between 5 and 9 °C and the onset likely took global warming on the Earth system, including both hydrological and associated biogeochemical feedbacks, and proxy data from the PETM can provide constraints on changes in warm climate hydrology simulated by general circulation models (GCMs). In this paper, we provide a critical review of biological and geochemical signatures interpreted as direct or indirect indicators of hydrological change at the PETM, explore the importance of adopting multi-proxy approaches, and present a preliminary model-data comparison. Hydrological records complement those of temperature and indicate that the climatic response at the PETM was complex, with significant regional and temporal variability. This is further illustrated by the biogeochemical consequences of inferred changes in hydrology and, in fact, changes in precipitation and the biogeochemical consequences are often conflated in geochemical signatures. There is also strong evidence in many regions for changes in the episodic and/or intra-annual distribution of precipitation that has not widely been considered when comparing proxy data to GCM output. Crucially, GCM simulations indicate that the response of the hydrological cycle to the PETM was heterogeneous - some regions are associated with increased precipitation - evaporation (P - E), whilst others are characterised by a decrease. Interestingly, the majority of proxy data come from the regions where GCMs predict an increase in PETM precipitation. We propose that comparison of hydrological proxies to GCM output can be an important test of model skill, but this will be enhanced by further data from regions of model-simulated aridity and simulation of extreme precipitation events.
Evaluating CO2 and CH4 dynamics of Alaskan ecosystems during the Holocene Thermal Maximum
He, Yujie; Jones, Miriam C.; Zhuang, Qianlai; Bochicchio, Christopher; Felzer, B. S.; Mason, Erik; Yu, Zicheng
2014-01-01
The Arctic has experienced much greater warming than the global average in recent decades due to polar amplification. Warming has induced ecological changes that have impacted climate carbon-cycle feedbacks, making it important to understand the climate and vegetation controls on carbon (C) dynamics. Here we used the Holocene Thermal Maximum (HTM, 11–9 ka BP, 1 ka BP = 1000 cal yr before present) in Alaska as a case study to examine how ecosystem Cdynamics responded to the past warming climate using an integrated approach of combining paleoecological reconstructions and ecosystem modeling. Our paleoecological synthesis showed expansion of deciduous broadleaf forest (dominated by Populus) into tundra and the establishment of boreal evergreen needleleaf and mixed forest during the second half of the HTM under a warmer- and wetter-than-before climate, coincident with the occurrence of the highest net primary productivity, cumulative net ecosystem productivity, soil C accumulation and CH4 emissions. These series of ecological and biogeochemical shifts mirrored the solar insolation and subsequent temperature and precipitation patterns during HTM, indicating the importance of climate controls on C dynamics. Our simulated regional estimate of CH4 emission rates from Alaska during the HTM ranged from 3.5 to 6.4 Tg CH4 yr−1 and highest annual NPP of 470 Tg C yr−1, significantly higher than previously reported modern estimates. Our results show that the differences in static vegetation distribution maps used in simulations of different time slices have greater influence on modeled C dynamics than climatic fields within each time slice, highlighting the importance of incorporating vegetation community dynamics and their responses to climatic conditions in long-term biogeochemical modeling.
Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum
Denis, E. H.; Pedentchouk, N.; Schouten, S.; Pagani, M.; Freeman, K. H.
2016-12-01
Fire, an important component of ecosystems at a range of spatial and temporal scales, affects vegetation distribution, the carbon cycle, and climate. In turn, climate influences fuel composition (e.g., amount and type of vegetation), fuel availability (e.g., vegetation that can burn based on precipitation and temperature), and ignition sources (e.g., lightning). Climate studies predict increased wildfire activity in future decades, but mechanisms that control the relationship between climate and fire are complex. Reconstructing environmental conditions during past warming events (e.g., the Paleocene-Eocene Thermal Maximum (PETM)) will help elucidate climate-vegetation-fire relationships that are expressed over long durations (1,000 - 10,000 yrs). The abrupt global warming during the PETM dramatically altered vegetation and hydrologic patterns, and, possibly, fire occurrence. To investigate coincident changes in climate, vegetation, and fire occurrence, we studied biomarkers, including polycyclic aromatic hydrocarbons (PAHs), terpenoids, and alkanes from the PETM interval at IODP site 302 (the Lomonosov Ridge) in the Arctic Ocean. Both pollen and biomarker records indicate angiosperms abundance increased during the PETM relative to gymnosperms, reflecting a significant ecological shift to angiosperm-dominated vegetation. PAH abundances increased relative to plant biomarkers throughout the PETM, which suggests PAH production increased relative to plant productivity. Increased PAH production associated with the angiosperm vegetation shift indicates a greater prevalence of more fire-prone species. A time lag between increased moisture transport (based on published δD of n-alkanes data) to the Arctic and increased angiosperms and PAH production suggests wetter conditions, followed by increased air temperatures, favored angiosperms and combined to enhance fire occurrence.
Transient dwarfism of soil fauna during the Paleocene-Eocene Thermal Maximum
Smith, J.J.; Hasiotis, S.T.; Kraus, M.J.; Woody, D.T.
2009-01-01
Soil organisms, as recorded by trace fossils in paleosols of the Willwood Formation, Wyoming, show significant body-size reductions and increased abundances during the Paleocene-Eocene Thermal Maximum (PETM). Paleobotanical, paleopedologic, and oxygen isotope studies indicate high temperatures during the PETM and sharp declines in precipitation compared with late Paleocene estimates. Insect and oligochaete burrows increase in abundance during the PETM, suggesting longer periods of soil development and improved drainage conditions. Crayfish burrows and molluscan body fossils, abundant below and above the PETM interval, are significantly less abundant during the PETM, likely because of drier floodplain conditions and lower water tables. Burrow diameters of the most abundant ichnofossils are 30-46% smaller within the PETM interval. As burrow size is a proxy for body size, significant reductions in burrow diameter suggest that their tracemakers were smaller bodied. Smaller body sizes may have resulted from higher subsurface temperatures, lower soil moisture conditions, or nutritionally deficient vegetation in the high-CO2 atmosphere inferred for the PETM. Smaller soil fauna co-occur with dwarf mammal taxa during the PETM; thus, a common forcing mechanism may have selected for small size in both above- and below-ground terrestrial communities. We predict that soil fauna have already shown reductions in size over the last 150 years of increased atmospheric CO2 and surface temperatures or that they will exhibit this pattern over the next century. We retrodict also that soil fauna across the Permian-Triassic and Triassic-Jurassic boundary events show significant size decreases because of similar forcing mechanisms driven by rapid global warming.
Occurrence of gigantic biogenic magnetite during the Paleocene-Eocene Thermal Maximum
Schumann, D.; Raub, T. D.; Kopp, R. E.; Guerquin-Kern, J. L.; Wu, T. D.; Rouiller, I.; Smirnov, A. V.; Sears, S. K.; Lücken, U.; Tikoo, S. M.; Hesse, R.; Kirschvink, J. L.; Vali, H.
2009-04-01
The Paleocene-Eocene Thermal Maximum (PETM) is one of the most severe climatic events of the Cenozoic Era. A massive injection of light carbon into the oceans and atmosphere over a few thousand of years triggered drastic perturbation of Earth's climate resulting in abrupt global warming of ~5-9oC [Sluijs et al., 2007] that persisted for ~180,000 years. This episode is marked by the diversification and radiation of terrestrial plants and mammals while in the marine realm numerous deep-sea benthic foraminifera species disappeared and new forms evolved. Sediments deposited during the PETM are clay-rich and contain distinct evidence of these climatic changes. Kopp et al., (2007) and Lippert & Zachos (2007) report an extraordinary magnetofossil ‘Lagerstätte' in lowermost Eocene kaolinite-rich clay sediments deposited at subtropical paleolatitude in the Atlantic Coastal Plain of New Jersey, USA. Magnetofossils are magnetic particles produced most abundantly by magnetotactic bacteria. Kopp et al. (2007) and Lippert & Zachos (2007) used ferromagnetic resonance (FMR) spectroscopy, other rock magnetic methods, and transmission electron microscopy (TEM) of magnetic separates to characterize sediments from boreholes at Ancora (ODP Leg 174AX) and Wilson Lake, NJ, respectively. These sediments contain abundant ~40- to 300-nm cuboidal, elongate-prismatic and bullet-shaped magnetofossils, sometimes arranged in short chains, resembling crystals in living magnetotactic bacteria. Despite the scarcity of intact magnetofossil chains, the asymmetry ratios of the FMR spectra reflects a profusion of elongate single domain (SD) crystals and/or chains. Here we address both conundrums by reporting the discovery from these same sediments of exceptionally large and novel biogenic magnetite crystals unlike any previously reported from living organisms or from sediments. Aside from abundant bacterial magnetofossils, electron microscopy reveals novel spearhead-like and spindle-like magnetite
Evaluating feedback time delay during perturbed and unperturbed balance in handstand.
Blenkinsop, Glen M; Pain, Matthew T G; Hiley, Michael J
2016-08-01
Feedback delays in balance are often assessed using muscle activity onset latencies in response to discrete perturbations. The purpose of the study was to calculate EMG latencies in perturbed handstand, and determine if delays are different to unperturbed handstand. Twelve national level gymnasts completed 12 perturbed and 10 unperturbed (five eyes open and five closed) handstands. Forearm EMG latencies during perturbed handstands were assessed against delay estimates calculated via: cross correlations of wrist torque and COM displacement, a proportional and derivative model of wrist torque and COM displacement and velocity (PD model), and a PD model incorporating a passive stiffness component (PS-PD model). Delays from the PD model (161±14ms) and PS-PD model (188±14ms) were in agreement with EMG latencies (165±14ms). Cross correlations of COM displacement and wrist torque provided unrealistically low estimates (5±9ms). Delays were significantly lower during perturbed (188±14ms) compared to unperturbed handstand (eyes open: 207±12ms; eyes closed: 220±19ms). Significant differences in delays and model parameters between perturbed and unperturbed handstand support the view that balance measures in perturbed testing should not be generalised to unperturbed balance.
无
2010-01-01
In this paper,constructal optimization of the twice Y-shaped assemblies of fins with six freedom degrees (characteristic parameters of geometry) is performed by employing finite element method and taking dimensionless maximum thermal resistance as a performance index,and the heat transfer performance of the twice Y-shaped assemblies of fins under various conditions with different freedom degrees are analyzed. The results show that the twice assemblies can improve the heat transfer performance of Y-shaped fin remarkably,and the minimum maximum thermal resistance of the twice Y-shaped assemblies of fins decreases by 36.37% compared with that of once Y-shaped assembly of fins. It is also proved again that the larger the number of freedom degrees for evolving is,the more perfect the system performance is. The effects of different characteristic parameters of geometry on the performance of the twice Y-shaped assemblies of fins are different,one should pay different attention to these parameters in practical engineering designs. The effects of two angles on the maximum thermal resistance are larger,but the optima of the two angles are robust. The effects of two height ratios on the maximum thermal resistance are more remarkable than those of two thickness ratios.
Paleocene-Eocene Thermal Maximum triggered by Volcanism revealed by Mercury anomalies
Khozyem, Hassan; Adatte, Thierry; Mbabi Bitchong, André; Chevalier, Yoann; Keller, Gerta
2017-04-01
The Paleocene-Eocene Thermal Maximum (PETM, 55.8±0.2 Ma) is marked by a global drop of 2-6‰ in 13C values and rapid warming of 4-5°C in tropical surface waters and 4-8°C in high latitudes. Climate warming persisted for several tens of thousands of years and resulted in rapid diversification in terrestrial mammals and marine planktic foraminifera. Deep-water bathyal benthic foraminifera suffered a mass extinction ( 40% species) but no significant extinctions occurred shallow shelf environments. Benthic extinctions are commonly explained as the effects of the initial stage of climate warming due to North Atlantic Volcanic Province volcanism (NAVP), which triggered methane release from ocean sediments causing global warming and ocean acidification. But the relationship between NAPV and the PETM events are not clearly demonstrated. Several studies [1-4] demonstrated the relationship between Hg anomalies in sediments and LIP activity associated with mass extinctions. We investigated the mercury (Hg) content of several sections located in deep bathyal (Zumaya, Trabakua, N-Spain) and outer shelf environments (Dababiya GSSP, Duwi, Egypt). At Zumaya the PETM is marked by a red clayey and marly interval poor in organic matter and coincident with a pronounced ∂13C negative shift. A comparable clay interval with low TOC content is also present in the Dababyia section in the lower part of the negative ∂13C shift, whereas the upper part of is enriched in TOC, reflecting increased productivity. A significant but unique Hg enrichment is observed at the onset of the PETM just below the carbone isotope shift in Spain as well as in Egypt. This increase, which is not correlated with clay or total organic carbon contents, suggests the Hg anomaly resulted from higher atmospheric Hg input into the marine realm, rather than organic matter scavenging and/or increased run-off. This Hg anomaly at the onset of the PETM provides the first direct evidence that volcanism played a
Wing, S. L.
2009-12-01
The Paleocene-Eocene Thermal Maximum (PETM) is an interval of global warming lasting ~150 ka that occurred at the start of the Eocene, ~55.8 Ma. Globally, temperature rose 4-8 °C in association with carbon cycle changes attributed to the release of >5,000 Pg of C into the ocean-atmosphere system. Fossil plants from the PETM in the Bighorn Basin, northwestern Wyoming, show that latest Paleocene forests contained palms, deciduous taxodiaceous conifers, and a variety of deciduous and evergreen angiosperms, many belonging to lineages with north temperate distributions. Mean annual temperature (MAT) for the latest Paleocene inferred from leaf margin analysis is ~18 °C. Early and mid-PETM floras have a completely different composition. They lack conifers and broad-leaved deciduous taxa with north temperate distributions, and are dominated by palms, legumes, and other angiosperm taxa with living relatives in the dry tropical forests of Central and South America. Leaf margin analysis gives an MAT of ~23 °C. Floras of this type are known from a stratigraphic interval ~30 m thick that also produces geochemical and mammalian faunal indicators of the PETM. Floras from late PETM or earliest post-PETM time are composed largely of species that had been present in the latest Paleocene, with a few new species that are common in the early Eocene. The inferred MAT is ~18 °C. Leaf size data suggest that the PETM was drier than the immediately preceding and following times. Floral data from the Bighorn Basin indicate that the magnitude of temperature change in this mid-latitude continental interior was similar to that inferred for the surface ocean. Evidence for dryness or seasonal dryness during the PETM has been observed in sections in northern Spain as well as in Wyoming, raising the possibility of widespread water stress in the middle northern latitudes. Change in floral composition during the PETM is consistent with regional extinction in mid-latitude populations of plants
Resilient terrestrial ecosystems at the Paleocene-Eocene Thermal Maximum (Invited)
Wing, S.
2010-12-01
The Paleocene-Eocene Thermal Maximum (PETM) was an interval of global warming lasting ~200 ka that began ~56 Ma. Global temperature rose 5-8 °C in association with the emission of thousands of Pg of carbon into the ocean-atmosphere system. PETM rocks and fossils are extensively exposed in the SE Bighorn Basin of Wyoming, where the event is represented by ~40 m of fluvial rocks. Fossil plants demonstrate a rapid and nearly complete turnover in floral composition that also suggests a change in the structure of vegetation. Floras collected from the last ~50 ka of the Paleocene are composed of Platanaceae (sycamores), Betulaceae (birches), Fagaceae (oaks), Lauraceae (laurels), Juglandaceae (walnuts), Cercidiphyllaceae (katsura), Taxodiaceae (dawn redwood), and Arecaceae (palms), among others. Many of these families are most diverse and abundant today in temperate to subtropical, mid-latitude forests. During the body of the carbon isotope excursion (CIE) associated with the PETM fossil floras have a completely different composition. All of the latest Paleocene plant types are absent, except for palms, and instead the floras are dominated by Fabaceae (bean family). Other taxa include Sapindaceae (soapberry), Annonaceae (paw-paw), and Hernandiaceae. Where living relatives are known, they live in dry tropical forests of Central and South America. This floral composition is maintained through the ~30 m of section representing the ~110 ka-long body of the CIE, the same interval characterized by dwarfed mammalian faunas. During the recovery phase of the CIE most of the latest Paleocene plants returned to the area of study, although some new taxa appeared, apparently coming in from Europe or Asia. The distinctive PETM floral types are not seen after the recovery phase of the CIE. Change in floral composition during the PETM apparently represents regional extirpations of populations of plants that preferred warm, mesic conditions, and northward range extensions of plants that
Paleohydrologic change across the Paleocene-Eocene Thermal Maximum, Bighorn Basin, WY
Baczynski, A. A.; McInerney, F. A.; Wing, S. L.; Kraus, M. J.
2013-12-01
One of the uncertainties in accurately predicting future climate change involves how the hydrologic cycle will respond to increasing pCO2 and temperature. Quantifying the relationship between carbon cycle perturbations and the hydrologic cycle in the geologic past is crucial to understanding and accurately modeling how anthropogenic carbon emissions will affect future changes in the hydrologic cycle. Records of paleohydrologic response to global warming in the geologic past are rare, particularly for continental interiors, where climate model projections of precipitation are highly uncertain. Here we examine hydrogen isotope ratios of leaf waxes as a tool for reconstructing paleohydrologic change in the continental interior of North America across the Paleocene-Eocene Thermal Maximum (PETM), an abrupt, transient episode of extreme global warming ~56 Ma. New hydrogen isotope measurements of leaf-wax n-alkanes from the southeastern Bighorn Basin, Wyoming record two positive shifts during the PETM. n-Alkane δD values first shift to more positive values just after the onset of the carbon isotope excursion and then again higher up in the body of the carbon isotope excursion, with a return to slightly more negative δD values in between. Paleobotanical, paleopedologic, and isotope data from the same field area have suggested that the Bighorn Basin may have experienced a drier or more seasonally dry climate during the PETM. Mean annual precipitation estimates based on paleosol major oxides, soil wetness assessed using the soil morphology index, and an aridity proxy based on differences in δ18O values of tooth enamel in aridity-sensitive and aridity-insensitive mammals each independently suggest a potential two-phase drying within the PETM interval. Similarly, the hydrogen isotope record could reflect two periods of drying, with a return to slightly wetter conditions in between. However, leaf-wax hydrogen isotope ratios reflect not only source water hydrogen isotope
Clyde, William C.; Gingerich, Philip D.
1998-11-01
New stratigraphic and paleontological information from the McCullough Peaks, northern Bighorn Basin, Wyoming, is incorporated into an isotaphonomic faunal database and used to investigate the impact of the latest Paleocene thermal maximum and coincident earliest Wasatchian immigration event on local mammalian community structure. Surface collections from Willwood Formation overbank deposits provide taphonomically consistent and stratigraphically resolved samples of the medium- to large-sized components of underlying mammalian communities. Rarefaction shows that the immigration event caused an abrupt and dramatic increase in species richness and evenness. After this initial increase, diversity tapered off to more typical Wasatchian levels that were still higher than those in the preceding Clarkforkian. Wasatchian immigrants were rapidly incorporated into the new community organization, representing ˜20% of the taxa and ˜50% of the individuals. Immigrant taxa generally had larger body sizes and more herbivorous and frugivorous dietary habits compared to endemic taxa, causing significant turnover in body-size structure and trophic structure. There was a significant short-term body-size decrease in many lineages that may have been prompted by the elevated temperatures and/or decreased latitudinal thermal gradients during the latest Paleocene thermal maximum. Rapid short-term climatic change (transient climates) and associated biotic dispersal can have abrupt and long-lasting effects on mammalian community evolution.
SAMPLEX: Automatic mapping of perturbed and unperturbed regions of proteins and complexes
Loth Karine
2010-01-01
Full Text Available Abstract Background The activity of proteins within the cell is characterized by their motions, flexibility, interactions or even the particularly intriguing case of partially unfolded states. In the last two cases, a part of the protein is affected either by binding or unfolding and the detection of the respective perturbed and unperturbed region(s is a fundamental part of the structural characterization of these states. This can be achieved by comparing experimental data of the same protein in two different states (bound/unbound, folded/unfolded. For instance, measurements of chemical shift perturbations (CSPs from NMR 1H-15N HSQC experiments gives an excellent opportunity to discriminate both moieties. Results We describe an innovative, automatic and unbiased method to distinguish perturbed and unperturbed regions in a protein existing in two distinct states (folded/partially unfolded, bound/unbound. The SAMPLEX program takes as input a set of data and the corresponding three-dimensional structure and returns the confidence for each residue to be in a perturbed or unperturbed state. Its performance is demonstrated for different applications including the prediction of disordered regions in partially unfolded proteins and of interacting regions in protein complexes. Conclusions The proposed approach is suitable for partially unfolded states of proteins, local perturbations due to small ligands and protein-protein interfaces. The method is not restricted to NMR data, but is generic and can be applied to a wide variety of information.
Amauris Gilbert-Hernández
2016-05-01
Full Text Available A procedure for the selection of maximum pipe thickness to achieve efficient thermal insulation in piping with steam tracing was developed. The bibliographical review allowed identifying the limitations of previous investigations with regard to the selection of pipe thickness in transfer systems with steam tracing. The model for calculating the overall lost heat was prepared. The procedure considers economic criteria for the selection of pipe thickness and established an optimal thickness value which guarantees a total minimum cost by establishing a balance between the expenditures resulting from heat loss and the project costs.
Pushing desalination recovery to the maximum limit: Membrane and thermal processes integration
Shahzad, Muhammad Wakil
2017-05-05
The economics of seawater desalination processes has been continuously improving as a result of desalination market expansion. Presently, reverse osmosis (RO) processes are leading in global desalination with 53% share followed by thermally driven technologies 33%, but in Gulf Cooperation Council (GCC) countries their shares are 42% and 56% respectively due to severe feed water quality. In RO processes, intake, pretreatment and brine disposal cost 25% of total desalination cost at 30–35% recovery. We proposed a tri-hybrid system to enhance overall recovery up to 81%. The conditioned brine leaving from RO processes supplied to proposed multi-evaporator adsorption cycle driven by low temperature industrial waste heat sources or solar energy. RO membrane simulation has been performed using WinFlow and IMSDesign commercial softwares developed by GE and Nitto. Detailed mathematical model of overall system is developed and simulation has been conducted in FORTRAN. The final brine reject concentration from tri-hybrid cycle can vary from 166,000ppm to 222,000ppm if RO retentate concentration varies from 45,000ppm to 60,000ppm. We also conducted economic analysis and showed that the proposed tri-hybrid cycle can achieve highest recovery, 81%, and lowest energy consumption, 1.76kWhelec/m3, for desalination reported in the literature up till now.
Relating a calcium indicator signal to the unperturbed calcium concentration time-course
Abarbanel Henry DI
2007-02-01
Full Text Available Abstract Background Optical indicators of cytosolic calcium levels have become important experimental tools in systems and cellular neuroscience. Indicators are known to interfere with intracellular calcium levels by acting as additional buffers, and this may strongly alter the time-course of various dynamical variables to be measured. Results By investigating the underlying reaction kinetics, we show that in some ranges of kinetic parameters one can explicitly link the time dependent indicator signal to the time-course of the calcium influx, and thus, to the unperturbed calcium level had there been no indicator in the cell.
Blaschek, M.; Renssen, H.
2012-01-01
The relatively warm early Holocene climate in the Nordic Seas, known as the Holocene Thermal Maximum (HTM), is often associated with an orbitally forced summer insolation maximum at 10 ka BP. The spatial and temporal response recorded in proxy data in the North Atlantic and the Nordic Seas reveal a
DeVries, Zachary C; Kells, Stephen A; Appel, Arthur G
2016-07-01
Evaluating the critical thermal maximum (CTmax) in insects has provided a number of challenges. Visual observations of endpoints (onset of spasms, loss of righting response, etc.) can be difficult to measure consistently, especially with smaller insects. To resolve this problem, Lighton and Turner (2004) developed a new technique: thermolimit respirometry (TLR). TLR combines real time measurements of both metabolism (V·CO2) and activity to provide two independent, objective measures of CTmax. However, several questions still remain regarding the precision of TLR and how accurate it is in relation to traditional methods. Therefore, we evaluated CTmax of bed bugs using both traditional (visual) methods and TLR at three important metabolic periods following feeding (1d, 9d, and 21d). Both methods provided similar estimates of CTmax, although traditional methods produced consistently lower values (0.7-1°C lower than TLR). Despite similar levels of precision, TLR provided a more complete profile of thermal tolerance, describing changes in metabolism and activity leading up to the CTmax, not available through traditional methods. In addition, feeding status had a significant effect on bed bug CTmax, with bed bugs starved 9d (45.19[±0.20]°C) having the greatest thermal tolerance, followed by bed bugs starved 1d (44.64[±0.28]°C), and finally bed bugs starved 21d (44.12[±0.28]°C). Accuracy of traditional visual methods in relation to TLR is highly dependent on the selected endpoint; however, when performed correctly, both methods provide precise, accurate, and reliable estimations of CTmax.
Unperturbed posttranscriptional regulatory Rev protein function and HIV-1 replication in astrocytes.
Ashok Chauhan
Full Text Available Astrocytes protect neurons, but also evoke proinflammatory responses to injury and viral infections, including HIV. There is a prevailing notion that HIV-1 Rev protein function in astrocytes is perturbed, leading to restricted viral replication. In earlier studies, our finding of restricted viral entry into astrocytes led us to investigate whether there are any intracellular restrictions, including crippled Rev function, in astrocytes. Despite barely detectable levels of DDX3 (Rev-supporting RNA helicase and TRBP (anti-PKR in primary astrocytes compared to astrocytic cells, Rev function was unperturbed in wild-type, but not DDX3-ablated astrocytes. As in permissive cells, after HIV-1 entry bypass in astrocytes, viral-encoded Tat and Rev proteins had robust regulatory activities, leading to efficient viral replication. Productive HIV-1 infection in astrocytes persisted for several weeks. Our findings on HIV-1 entry bypass in astrocytes demonstrated that the intracellular environment is conducive to viral replication and that Tat and Rev functions are unperturbed.
Miyabe, Masabumi; Ohba, Masaki; Wakaida, Ikuo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1997-10-01
Autoionizing Rydberg series converging to six states (0, 261.841, 633.273, 3082.011, 3427.274, 3444.235 cm{sup -1}) of Gd ion have been observed by using three-color three-step photoionization via ten different 2nd-step levels of J=0 or 1. While the perturbations with interlopers become significant in the region of n=30-35 for most of the observed series, long and well-defined series structures appeared in higher energy region. From an analysis of such unperturbed structures, the first ionization potential of Gd atom was estimated to be 49601.45 (30) cm{sup -1}. This is in good agreement with the previous value, but the accuracy is improved by about one order of magnitude. In addition, isotope effect on the ionization potential was also determined by isotope shifts of some Rydberg series. (author)
Barkin, Yu. V.
New unperturbed motions are suggested for the study of the rotational motion of deformable celestial bodies. This motion describes the rotation of an isolated celestial body deformed by its own rotation. By some natural simplifications and by using special forms of canonical variables (similar to Andoyer's variables) the problem is reduced to the classical Euler-Poinsot problem for a rigid body, but with different moments of inertia. The suggested unpertubed motion describes Chandler's pole motion and we shall call it Chandler or Euler-Chandler motion. The development of the unperturbed theory is described in this paper. The solution of the Chandler problem (Andoyer's variables, components of angular velocity of the body's axes, and their direction cosines) is presented in elliptical and - functions, and in the form of Fourier series in the angle-action variables. Similar Fourier series were obtained for products and squares of the diraction cosines. The coefficients of these series are expressed through full elliptical integrals of the first, second and third kinds with modulus which is the defining function of the action variables. It is the principal peculiarity of these series. As an illustration we give a application of this unperturbed theory to the study of the Earth's rotation (the principal properties of the Earth's rotation and perturbations). So, the unperturbed motion describes the following phenomena of the Earth's rotation: Chandler's motion of the pole of the Earth's axis of rotation; the ellipticity of the trajectory of the Earth's pole; the non-uniformity of the pole motion along the elliptical trajectory; the variation with Chandler's period of the modulus of the Earth's angular velocity. Theory of the perturbed rotational motion of the Earth is constructed on the basis of the special forms of equations of the rotation of a deformable body (in angle-action variables and their modifications for the Chandler-Euler problem). For the construction of
A feedback-based inverse heat transfer method to estimate unperturbed temperatures in wellbores
Espinosa-Paredes, Gilberto [Area de Ingenieria en Recursos Energeticos, Universidad Autonoma Metropolitana-Iztapalapa, Apartado Postal 55-534, Mexico D.F. 09340 (Mexico); Espinosa-Martinez, Erick G. [Retorno Quebec 6, Col. Burgos de Cuernavaca 62580, Temixco, Mor. (Mexico)
2009-01-15
This paper presents a feedback-based strategy to solve an inverse heat transfer problem for the estimation of unperturbed formation temperatures (UFT) from measured temperatures in wellbores. The feedback function uses the error between the measured and estimated temperatures during the shut-in process. Thus, an inverse heat transfer problem was solved in this way since the UFT represents the unknown initial conditions and the measured temperatures in the wellbore represents the particular solution of the PDE'S governing the heat transfer process in the formation and in the wellbore system. The performance of the method is illustrated via numerical simulations of two wells: (a) oil well FE-1227 from the Gulf of Mexico maritime zone and (b) well CP-0512 from Cerro Prieto Mexican geothermal field. (author)
Davit Vasilyan
Full Text Available BACKGROUND: The oldest and largest member of giant salamanders (Cryptobranchidae Aviturus exsecratus appears in the latest Paleocene (near the Paleocene-Eocene Thermal Maximum of Mongolia. Based on femoral and vertebral morphology and metrics, a terrestrial adaptation has been supposed for this species. METHODOLOGY/PRINCIPAL FINDINGS: A detailed morphological reinvestigation of published as well as unpublished material reveals that this salamander shows a vomerine dentition that is posteriorly shifted and arranged in a zigzag pattern, a strongly developed olfactory region within the cranial cavity, and the highest bone ossification and relatively longest femur among all fossil and recent cryptobranchids. CONCLUSIONS/SIGNIFICANCE: The presence of these characteristics indicates a peramorphic developmental pattern for Aviturus exsecratus. Our results from Av. exsecratus indicate for the first time pronounced peramorphosis within a crown-group lissamphibian. Av. exsecratus represents a new developmental trajectory within both fossil and recent lissamphibian clades characterized by extended ontogeny and large body size, resembling the pattern known from late Paleozoic eryopines. Moreover, Av. exsecratus is not only a cryptobranchid with distinctive peramorphic characters, but also the first giant salamander with partially terrestrial (amphibious lifestyle. The morphology of the vomers and dentaries suggests the ability of both underwater and terrestrial feeding.
Self-Trail, Jean; Robinson, Marci M.; Bralower, Timothy J.; Sessa, Jocelyn A.; Hajek, Elizabeth A.; Kump, Lee R.; Trampush, Sheila M.; Willard, Debra A.; Edwards, Lucy E.; Powars, David S.; Wandless, Gregory A.
2017-01-01
The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30–100 m water depth) site in the Salisbury Embayment. Observations indicate that at the onset of the PETM, the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low-oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12C-enriched CO2. We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.
Self-Trail, Jean M.; Robinson, Marci M.; Bralower, Timothy J.; Sessa, Jocelyn A.; Hajek, Elizabeth A.; Kump, Lee R.; Trampush, Sheila M.; Willard, Debra A.; Edwards, Lucy E.; Powars, David S.; Wandless, Gregory A.
2017-07-01
The Paleocene-Eocene Thermal Maximum (PETM) was an interval of extreme warmth that caused disruption of marine and terrestrial ecosystems on a global scale. Here we examine the sediments, flora, and fauna from an expanded section at Mattawoman Creek-Billingsley Road (MCBR) in Maryland and explore the impact of warming at a nearshore shallow marine (30-100 m water depth) site in the Salisbury Embayment. Observations indicate that at the onset of the PETM, the site abruptly shifted from an open marine to prodelta setting with increased terrestrial and fresh water input. Changes in microfossil biota suggest stratification of the water column and low-oxygen bottom water conditions in the earliest Eocene. Formation of authigenic carbonate through microbial diagenesis produced an unusually large bulk carbon isotope shift, while the magnitude of the corresponding signal from benthic foraminifera is similar to that at other marine sites. This proves that the landward increase in the magnitude of the carbon isotope excursion measured in bulk sediment is not due to a near instantaneous release of 12C-enriched CO2. We conclude that the MCBR site records nearshore marine response to global climate change that can be used as an analog for modern coastal response to global warming.
Morsi, Abdel-Mohsen M.; Speijer, Robert P.; Stassen, Peter; Steurbaut, Etienne
2011-02-01
Two outcrop sections spanning the Paleocene-early Eocene boundary in the Sidi Nasseur-Wadi Mezaz area in northwest Tunisia provided rich ostracode assemblages, yielding 26 species of which three are newly described: Reymenticosta bassiounii, Reymenticosta nasseurensis and Buntonia? tunisiensis. The recorded ostracode fauna and associated foraminifera reflect deposition in a coastal to inner neritic environment. Many of the recorded taxa have a wide geographic distribution throughout the Middle East and North Africa. A correspondence is also observed with West African faunas, especially in the early Eocene fauna. These taxa seem to have originated in West Africa during the Paleocene and migrated northwards during the late Paleocene to early Eocene. Sea-level change and decrease in oxygenation associated with the Paleocene-Eocene thermal maximum (PETM) caused the local disappearance of the South Tethyan Paleocene fauna represented by Paracosta kefensis (morphotype-A), Paracosta aff. paleomokattamensis, Paracypris sp. B Esker, Loxoconcha saharaensis, Buntonia sp. 3 Donze et al., Protobuntonia nakkadii, and probably Reymenticosta bassiounii and R. nasseurensis. Simultaneously, a new but poorly diverse Afro-Tethyan fauna, mainly represented by Alocopocythere attitogonensis and Buntonia? tunisiensis, settled in the studied part of the basin. After the PETM, diversity increased again as various taxa (e.g. Bairdia aegyptiaca, Reticulina lamellata and Aegyptiana duwiensis) (re)appeared. Although detailed records across the P/E boundary are still sparse, it appears that the PETM exerted significant influence on the paleobiogeography and composition of Tethyan ostracode faunas.
C. J. Hollis
2015-02-01
Full Text Available Re-examination of a sediment core collected by the Deep Sea Drilling Project (DSDP Site 277 on the western margin of the Campbell Plateau, Southwest Pacific Ocean (paleolatitude of ∼ 65° S, has identified an intact Paleocene–Eocene (P–E boundary overlain by a 34 cm-thick record of the initial phase of the Paleocene–Eocene Thermal Maximum (PETM within nannofossil chalk. The upper part of the PETM is truncated, either due to drilling disturbance or a sedimentary hiatus. An intact record of the onset of the PETM is indicated by a gradual decrease in δ13C values over 20 cm, followed by a 14 cm interval in which δ13C is 2‰ lighter than uppermost Paleocene values. After accounting for effects of diagenetic alteration, we use δ18O and Mg/Ca values from foraminiferal tests to determine that intermediate and surface waters warmed by ∼ 6° at the onset of the PETM prior to the full development of the negative δ13C excursion. After this initial warming, sea temperatures were relatively stable through the PETM, but declined abruptly across the unconformity that truncates the event at this site. Mg/Ca analysis of foraminiferal tests indicate peak intermediate and surface water temperatures of ∼ 19 and ∼ 32 °C, respectively. These temperatures may be influenced by enhanced poleward ocean heat transport during the PETM and surface water values may also be biased towards warm season temperatures.
A high-resolution record from Svalbard of carbon release during the Paleocene-Eocene Thermal Maximum
Cui, Y.; Kump, L. R.; Ridgwell, A.; Junium, C. K.
2009-12-01
The WUN-pACE team (http://www.wun.ac.uk/pACE/) has obtained core materials from a highly expanded section spanning the Paleocene Eocene Thermal Maximum (PETM) from the Arctic of Svalbard. Carbon isotopic analysis of the bulk organic matter extracted from core BH9-05 details the onset of the negative carbon isotope excursion (CIE) of approximately 4.5 permil over 5m of section (sampled every 30 cm). The entire excursion is 50m in thickness, and is nearly identical in shape and magnitude to the recently published orbitally tuned record from ODP Site 1263, allowing us to establish a tentative chronology for the core. Using this record to drive an intermediate complexity Earth-system model (Genie-1; http://www.genie.ac.uk), we determine the implied rates of carbon release at the Paleocene-Eocene boundary necessary to replicate the isotope excursion and assuming different alternative isotopic compositions for the possible sources of fossil carbon driving the excursion (methane clathrate, coal/peat/marine organic matter). We also assess the predicted response of the seafloor carbonate dissolution records to observations and evaluate the sensitivity of these results to the presumed initial conditions (ocean alkalinity and initial calcite compensation depths, which affect the ocean buffering capacity).
Tegner, C.; Heilmann-Clausen, C.; Larsen, R. B.; Kent, A. J. R.
2012-04-01
Massive flood basalt volcanism in the NE Atlantic 56 million years ago can be related to the initial manifestation of the Iceland plume and ensuing continental rifting, and has been correlated with a short (c. 200,000 years) global warming period, the Paleocene-Eocene thermal maximum (PETM). A hypothesis is that magmatic sills emplaced into organic-rich sediments on the Norwegian margin triggered rapid release of greenhouse gases. However, the largest exposed volcanic succession in the region, the E Greenland flood basalts provide additional details. The alkaline Ash-17 provides regional correlation of continental volcanism and pertubation of the oceanic environment. In E Greenland Ash-17 is interbedded with the uppermost part of the flood basalt succession. In the marine sections of Denmark, Ash-17 postdates PETM, most likely by 3-400,000 years. While radiometric ages bracket the duration of the main flood basalt event to less than a million years, the subsidence history of the Skaergaard intrusion due to flood basalt emplacement indicates it took less than 300,000 years. It is therefore possible that the main flood basalts in E Greenland postdates PETM. This is supported by a scarcity of ash layers within the PETM interval. Continental flood basalt provinces represent some of the highest sustained volcanic outputs preserved within the geologic record. Recent studies have focused on estimating the atmospheric loading of volatile elements and have led to the suggestion that they may be associated with significant global climate changes and mass extinctions. Estimates suggest that c. 400,000 km3 of basaltic lava erupted in E Greenland and the Faeroe islands. Based on measurements of melt inclusions and solubility models, approximately 3000 Gt of SO2 and 220 Gt of HCl were released by these basalts. Calculated yearly fluxes approach 10 Mt/y SO2 and 0.7 Mt/y HCl. Refinements of these estimates, based largely on further melt inclusion measurements, are proceeding. Our
Taking the pulse of the carbon release during the onset of the Paleocene-Eocene thermal maximum
Babila, T. L.; Bralower, T. J.; Robinson, M. M.; Self-Trail, J. M.; Zachos, J. C.
2015-12-01
The Paleocene-Eocene thermal maximum (PETM) (~55 Ma) is a warming event characterized by a negative carbon isotope excursion (CIE) representing a large and rapid injection of carbon into global reservoirs. Debate continues regarding the mechanism, magnitude, and tempo of the carbon released. A few terrestrial and marine sediment records document two distinct δ13C excursions a pre-onset excursion (POE) and CIE interpreted as evidence of multiple carbon injections. We generated geochemical records of ocean carbonate chemistry and temperature using cores drilled by the U.S Geological Survey (USGS) that recovered expanded sections of the PETM onset along the mid-Atlantic coastal plain. Our stable isotope (δ13C and δ18O) planktonic foraminifer records from South Dover Bridge (SDB), Maryland USA exhibit prominent anomalies across the Paleocene-Eocene boundary consistent to proximal coastal sites. δ13C records of mixed-layer (Acarinina spp.) and thermocline (Subbotina spp.) dwelling planktonic foraminifera show two negative carbon excursions that include a 2 ‰ POE and 3-4 ‰ CIE that return to baseline values between events in conjunction with bulk carbonate trends. Remarkably, contemporaneous foraminifer δ18O records exhibit only a minor response during the POE. This could be an artifact of preservation, or at face value, indicative of little to no warming. For the latter, this would require a rapid, but relatively small carbon release. To test the coupled link between atmosphere and surface ocean δ13C records we aim to integrate our geochemical results with model simulations to establish the duration and global extent of multiple carbon releases.
Royer, D. L.; Currano, E. D.; Wilf, P.; Wing, S. L.; Labandeira, C. C.; Lovelock, E. C.
2007-12-01
Deciphering the ecological impacts of climate change is a key priority for paleontologists and ecologists alike. An important ecological metric in vegetated settings is the leaf economics spectrum, which represents an adaptive continuum running from rapid resource acquisition to maximized resource retention. This spectrum is comprised of a large number of coordinated traits, including leaf mass per area (LMA), leaf lifespan, photosynthetic rate, nutrient concentration, and palatability to herbivores. Here we apply a recently developed technique for reconstructing LMA to a suite of four isotaphonomic fossil plant sites spanning the Paleocene-Eocene thermal maximum (PETM) in the Bighorn Basin, Wyoming, USA. This technique is based on the biomechanical scaling between petiole width and leaf mass, and it has been calibrated with 65 present-day sites from five continents and tested on two well-known Eocene fossil localities (Bonanza, Utah and Republic, Washington). There are no significant differences in LMA among plants across the PETM. This stasis is present despite a backdrop of extreme climate change during the PETM in this region, including a three-to-four-fold increase in atmospheric CO2, an ~5 °C rise in temperature, and possible drying. Moreover, quantitative measurements of insect herbivory show, on average, a two-fold increase during the PETM relative to before and after the event. We interpret our results to suggest that leaf-economic relationships can, in some situations, partially decouple. More specifically, our documented increase in insect herbivory during the PETM with no concomitant decrease in LMA implies that during this interval less carbon was being captured by plants per unit of investment. Because the rate and magnitude of climate change during the PETM is similar to present-day anthropogenic changes, our results may provide clues for predictions of ecological impacts in the near future.
Robinson, M. M.; Self-Trail, J. M.; Willard, D. A.; Stassen, P.; Spivey, W.
2015-12-01
The Paleocene-Eocene Thermal Maximum (PETM; ~55.5 Ma) is recognized globally in marine sediments by a carbonate dissolution zone, the extinction or turnover of benthic taxa, and a radiation of planktic excursion taxa, all accompanied by a rapid-onset, negative carbon isotope excursion (CIE). The cause and nature of the massive carbon release leading to this extreme climate event remains under debate. Regardless of cause, the environmental and ecosystem changes centered on the PETM are the subject of much study because they provide an analog to modern deteriorating conditions associated with the ongoing rise in atmospheric carbon dioxide. We present evidence from sediments of the South Dover Bridge core, deposited on the U.S. mid-Atlantic shelf, for an ocean acidification event in the latest Paleocene that coincides with a relatively small (-2‰) negative carbon isotope excursion (CIE) that precedes the larger (-4‰) Paleocene-Eocene CIE onset. Planktic foraminifers during this pre-onset event (POE) show post-deposition dissolution in which the coarsely cancellate and muricate wall textures characteristic of many Late Paleocene species have been dissolved away, leaving smooth, thin-walled specimens often with collapsed chambers. In addition, we document biotic responses in benthic, planktic, and terrestrial communities to the POE, including shifts in foraminifer and pollen assemblages and adaptations in calcareous nannofossil species in response to environmental perturbations. A complete recovery is evident between the POE and CIE in both the carbon isotopic signal and in the biotic response, providing additional evidence not only for a pulsed carbon release, but also for a more rapid rate of carbon release than is suggested by a single pulse over a longer period of time. The timing, nature and magnitude of ecological changes during the less extreme POE shallow water acidification event may help to define the ecological tipping point of shallow marine ecosystems.
Meissner, K. J.; Alexander, K.; Bralower, T. J.
2015-12-01
The Paleocene-Eocene Thermal Maximum, ˜55 million years before present, was a period of rapid warming marked by a negative carbon isotope excursion and widespread dissolution of seafloor carbonate. These changes have been attributed to a massive release of carbon into the exogenic carbon cycle, and thus, the event provides an analog for future climate and environmental changes given the current anthropogenic CO2 emissions. Previous attempts to constrain the amount of carbon released have produced widely diverging results, between 2000 and 10,000 gigatons carbon (GtC). Sediment records indicate that acidification of deep waters was generally more extensive and severe in the Atlantic and Caribbean regions, with more modest changes in the Southern and Pacific Oceans. Here we compare simulations integrated with the UVic Earth System Climate Model with reconstructions of temperature and dissolution to present a mechanism that might explain the observed spatial differences and to constrain the total mass of carbon released. Due to the late Paleocene topography, highly corrosive waters accumulate in the deep North Atlantic before the PETM in our simulations. Several thousand years into the event, deep ocean warming destabilizes the North Atlantic water column and triggers deep water formation. This causes the corrosive bottom water to spill over an equatorial sill into the South Atlantic and through the Southern and Pacific Oceans, progressively gaining alkalinity. The simulated pattern of sediment dissolution along the path taken by this corrosive water is consistent with most dissolution estimates made from CaCO3 measurements in the Paleocene-Eocene sediment record. We find two scenarios that agree best with proxy data: a carbon release of 7000 GtC in combination with pre-event atmospheric carbon dioxide concentrations of 840 ppm and a carbon release of 7000-10,000 GtC with pre-event CO2 concentrations of 1680 ppm.
Gingerich, P. D.
2012-12-01
Many important environmental events in the geological past were first recognized by their effects on the associated biota, and this is true for the Paleocene-Eocene Thermal Maximum or PETM global greenhouse warming event, which happened 55 million years before present. In the Southern Ocean, PETM carbon and oxygen isotope anomalies were found to coincide with a major terminal-Paleocene disappearance or extinction of benthic foraminiferans. On North America the PETM carbon isotope excursion (CIE) was found to coincide with mammalian dwarfing and a major initial-Eocene appearance or origination event of continental mammals. Linking the two records, marine and continental, resolved a long-standing disagreement over competing definitions of the Paleocene-Eocene epoch boundary, and more importantly indicated that the PETM greenhouse warming event was global. Dwarfing of herbivorous mammals can be interpreted as a response to elevated atmospheric CO2. The origin of modern orders of mammals including Artiodactyla, Perissodactyla, and Primates ('APP' taxa) is more complicated and difficult to explain but the origin of these orders may also be a response, directly or indirectly, to PETM warming. We now know from Polecat Bench and elsewhere in North America that the biotic response to PETM greenhouse warming involved the appearance of at least two new mammalian faunas distinct from previously known Clarkforkian mammals of the upper or late Paleocene and previously known Wasatchian mammals of the lower or early Eocene. Three stages and ages of the former are known (Cf-1 to Cf-3) and seven stages and ages of the latter are known (Wa-1 to Wa-7), each occupying about a hundred meters of strata representing a half-million years or so of time. Between the standard Clarkforkian and Wasatchian faunal zones is an initial 'Wa-M' faunal zone of only five or so meters in thickness and something on the order of 20 thousand years of geological time. The Wa-M fauna includes the first
Sluijs, A.; van Roij, L.; Harrington, G.J.; Schouten, S.; Sessa, J.A.; LeVay, L.J.; Reichart, G.-J.; Slomp, C.P.
2014-01-01
The Paleocene–Eocene Thermal Maximum (PETM, ~ 56 Ma) was a ~ 200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean–atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen concentrations
Sluijs, A.; van Roij, L.; Harrington, G.J.; Schouten, S.; Sessa, J.A.; LeVay, L.J.; Reichart, G.-J.; Slomp, C.P.
2014-01-01
The Paleocene–Eocene Thermal Maximum(PETM, ?56 Ma) was a ?200 kyr episode of globalwarming, associated with massive injections of 13C-depletedcarbon into the ocean–atmosphere system. Although climatechange during the PETM is relatively well constrained,effects on marine oxygen concentrations and nut
Kwang Seob Kim
2014-11-01
Full Text Available To estimate the contributions of feedforward vs. feedback control systems in speech articulation, we analyzed the correspondence between initial and final kinematics in unperturbed tongue and jaw movements for consonant-vowel (CV and vowel-consonant (VC syllables. If movement extents and endpoints are highly predictable from early kinematic information, then the movements were most likely completed without substantial online corrections (feedforward control; if the correspondence between early kinematics and final amplitude or position is low, online adjustments may have altered the planned trajectory (feedback control (Messier and Kalaska, 1999. Five adult speakers produced consonant-vowel (CV and vowel-consonant (VC syllables with high, mid, or low vowels while movements of the tongue and jaw were tracked electromagnetically. The correspondence between the kinematic parameters peak acceleration or peak velocity and movement extent as well as between the articulators’ spatial coordinates at those kinematic landmarks and movement endpoint was examined both for movements across different target distances (i.e., across vowel height and within target distances (i.e., within vowel height. Taken together, results suggest that jaw and tongue movements for these CV and VC syllables are mostly under feedforward control but with feedback-based contributions. One type of feedback-driven compensatory adjustment appears to regulate movement duration based on variation in peak acceleration. Results from a statistical model based on multiple regression are presented to illustrate how the relative strength of these feedback contributions can be estimated.
Giusberti, L.; Boscolo Galazzo, F.; Thomas, E.
2016-02-01
The Forada section (northeastern Italy) provides a continuous, expanded deep-sea record of the Paleocene-Eocene Thermal Maximum (PETM) in the central-western Tethys. We combine a new, high-resolution, benthic foraminiferal assemblage record with published calcareous plankton, mineralogical and biomarker data to document climatic and environmental changes across the PETM, highlighting the benthic foraminiferal extinction event (BEE). The onset of the PETM, occurring ˜ 30 kyr after a precursor event, is marked by a thin, black, barren clay layer, possibly representing a brief pulse of anoxia and carbonate dissolution. The BEE occurred within the 10 cm interval including this layer. During the first 3.5 kyr of the PETM, several agglutinated recolonizing taxa show rapid species turnover, indicating a highly unstable, CaCO3-corrosive environment. Calcareous taxa reappeared after this interval, and the next ˜9 kyr were characterized by rapid alternation of peaks in abundance of various calcareous and agglutinated recolonizers. These observations suggest that synergistic stressors, including deepwater CaCO3 corrosiveness, low oxygenation, and high environmental instability caused the extinction. Combined faunal and biomarker data (BIT index, higher plant n-alkane average chain length) and the high abundance of the mineral chlorite suggest that erosion and weathering increased strongly at the onset of the PETM, due to an overall wet climate with invigorated hydrological cycle, which led to storm flood events carrying massive sediment discharge into the Belluno Basin. This interval was followed by the core of the PETM, characterized by four precessionally paced cycles in CaCO3 %, hematite %, δ13C, abundant occurrence of opportunistic benthic foraminiferal taxa, and calcareous nannofossil and planktonic foraminiferal taxa typical of high-productivity environments, radiolarians, and lower δDn-alkanes. We interpret these cycles as reflecting alternation between an overall
Giusberti, L.; Boscolo Galazzo, F.; Thomas, E.
2015-09-01
The Forada section (northeastern Italy) provides a continuous, expanded deep-sea record of the Paleocene/Eocene thermal maximum (PETM) in the central-western Tethys. We combine a new, high resolution, benthic foraminiferal assemblage record with published calcareous plankton, mineralogical and biomarker data to document climatic and environmental changes across the PETM, highlighting the benthic foraminiferal extinction event (BEE). The onset of the PETM, occurring ~ 30 kyr after a precursor event, is marked by a thin, black, barren clay layer, possibly representing a brief pulse of anoxia and carbonate dissolution. The BEE occurred within the 10 cm interval including this layer. During the first 3.5 kyr of the PETM several agglutinated recolonizing taxa show rapid species turnover, indicating a highly unstable, CaCO3-corrosive environment. Calcareous taxa reappeared after this interval, and the next ~ 9 kyr were characterized by rapid alternation of peaks in abundance of various calcareous and agglutinant recolonizers. These observations suggest that synergistic stressors including deep water CaCO3-corrosiveness, low oxygenation, and high environmental instability caused the extinction. Combined faunal and biomarker data (BIT index, higher plant n-alkane average chain length) and the high abundance of the mineral chlorite suggest that erosion and weathering increased strongly at the onset of the PETM, due to an overall wet climate with invigorated hydrological cycle, which led to storm flood-events carrying massive sediment discharge into the Belluno Basin. This interval was followed by the core of the PETM, characterized by four precessionally paced cycles in CaCO3%, hematite%, δ13C, abundant occurrence of opportunistic benthic foraminiferal taxa, as well as calcareous nannofossil and planktonic foraminiferal taxa typical of high productivity environments, radiolarians, and lower δDn-alkanes. We interpret these cycles as reflecting alternation between an
Smith, Francesca A.; Wing, Scott L.; Freeman, Katherine H.
2007-10-01
Carbon-isotope measurements ( δ13C) of leaf-wax n-alkanes from the Paleocene-Eocene Thermal Maximum (PETM) in the Bighorn Basin, Wyoming, reveal a negative carbon isotope excursion (CIE) of 4-5‰, which is 1-2‰ larger than that observed in marine carbonate δ13C records. Reconciling these records requires either that marine carbonates fail to record the full magnitude of the CIE or that the CIE in plants has been amplified relative to the marine. Amplification of the CIE has been proposed to result from an increase in available moisture that allowed terrestrial plants to increase 13C-discrimination during the PETM. Leaf physiognomy, paleopedology and hydrogen isotope ratios of leaf-wax lipids from the Bighorn Basin, however, all suggest that rather than a simple increase in available moisture, climate alternated between wet and dry during the PETM. Here we consider two other explanations and test them quantitatively with the carbon isotopic record of plant lipids. The "marine modification" hypothesis is that the marine carbonate record was modified by chemical changes at the PETM and that plant lipids record the true magnitude of the CIE. Using atmospheric CO 2δ13C values estimated from the lipid record, and equilibrium fractionation between CO 2 and carbonate, we estimate the expected CIE for planktonic foraminifera to be 6‰. Instead, the largest excursion observed is about 4‰. No mechanism for altering marine carbonate by 2‰ has been identified and we thus reject this explanation. The "plant community change" hypothesis is that major changes in floral composition during the PETM amplified the CIE observed in n-alkanes by 1-2‰ relative to marine carbonate. This effect could have been caused by a rapid transition from a mixed angiosperm/conifer flora to a purely angiosperm flora. The plant community change hypothesis is consistent with both the magnitude and pattern of CIE amplification among the different n-alkanes, and with data from fossil plants
Carozza, D. A.; Mysak, L. A.
2012-04-01
The Paleocene-Eocene thermal maximum (PETM), approximately 55 million years ago, was a period of intense climate and environmental change that was associated with the release of unprecedented amounts of light carbon to the ocean-atmosphere system. This event is documented by large negative carbon isotope excursions (CIEs) in oceanic and terrestrial environments, by an abrupt shoaling of the lysocline and calcite compensation depth, and by significant increases in average global temperature. Due to its 13C-depleted isotopic composition and strong atmospheric radiative forcing, methane is thought to have played a pivotal role during the PETM. Recent high-resolution geochemical records indicate that the PETM has a more complex structure than was apparent in earlier records. In particular, ocean sediment cores indicate that the PETM CIE was composed of three notable excursions separated by two 20-ky periods of negligible del13C change. Moreover, a 3-ky warming period that occurred prior to the PETM CIE has indicated that the carbon release that caused the initial CIE may not have produced the initial warming, as was previously postulated and modeled.In this study, we couple an atmospheric methane box model to a box model of the global carbon cycle, which is tuned to the background state of the PETM, in order to constrain the carbon emission and assess the role of methane. The initial 4 ky of the PETM are modeled as two separate stages involving: 1) a gradual warming with little or no lysocline shoaling or CIE, and 2) an abrupt warming, lysocline shoaling, and a CIE. For each stage, a range of atmospheric and oceanic emission scenarios representing different amounts, rates, and isotopic content of emitted carbon are simulated, and then compared to the sedimentary record. The sensitivity of the results to changes in climate sensitivity, global temperature change, lysocline shoaling, CIE, and background carbon dioxide concentration, among other variables, is tested. We
Terrestrial records of Eocene Thermal Maximum 2 (ETM2 / H1 / Elmo) and H2 in the Bighorn Basin (USA)
Abels, H. A.; Clyde, W. C.; Gingerich, P. D.; Hilgen, F. J.; Fricke, H. C.; Bowen, G. J.; Lourens, L. J.
2012-04-01
Late Paleocene and early Eocene hyperthermal events are short-lived periods of rapid greenhouse warming related to massive increases in the concentration of atmospheric CO2. Eocene Thermal Maximum 2 (ETM2; also known as the Elmo event or H1) is the second largest of these events after the PETM and is followed after ~100 kyr by the smaller H2 event. ETM2 has only been documented in a few high-resolution marine successions and suggested in one low-resolution terrestrial record. Thus the impact of ETM2 on continental climates and biotas remains largely unknown. Recently, we located two successive negative carbon isotope excursions (CIEs) of ~3.8 and ~2.8 per mille in paleosol carbonate in the floodplain sedimentary record of the Bighorn Basin, Wyoming (USA). The C24r/C24n magnetochron boundary is pinpointed above the base of the larger CIE in our paleomagnetic results (Fig. 1). This stratigraphic position and the pattern and magnitude of the events indicate that the CIEs are the ETM2/H1 and H2 events, respectively. Mammal finds in the McCullough Peaks area where we documented the CIEs indicate that the Wa4-Wa5 biozone boundary occurs well below ETM2. If rapid faunal turnover at the Wa4-Wa5 boundary (known as 'biohorizon B') involved extinction of Ectocion and Haplomylus and the first appearance of Bunophorus, as commonly assumed, then faunal turnover at biohorizon B cannot be explained by greenhouse warming at the ETM2 hyperthermal event. Our new terrestrial carbon isotope record of ETM2/H1 and H2 reveals, when placed in an astronomically-calibrated timeframe, a very similar pattern to records recovered from marine successions. The magnitudes of the ongoing CIEs are similar to those found in western India that has been tentatively linked to ETM2. Also, the CIEs of PETM, ETM2, and H2 in paleosol carbonate records from the Bighorn Basin seem to scale linearly with CIEs in marine carbonate records from the same events.
McInerney, F. A.; Bloch, J. I.; Secord, R.; Wing, S. L.; Kraus, M. J.; Boyer, D. M.
2009-12-01
The Paleocene-Eocene Thermal Maximum (PETM) presents an opportunity to characterize continental hydrologic changes during rapid and extreme global warming. The Bighorn Basin, Wyoming, USA, has long been recognized for the PETM sequences preserved there and sits in an ideal location for recording hydrologic changes in the interior of North America. The southeast Bighorn Basin is of particular interest because it contains not only alluvial paleosols and vertebrate fossils, but also macrofloral remains from the PETM. The carbon isotope excursion associated with this event is preserved in this part of the Basin in leaf wax lipids, tooth enamel, and bulk organic matter. To characterize the hydrologic changes that occurred during the PETM we are applying a suite of isotopic, paleobotanical and paleopedological approaches to sections in the southeast Bighorn Basin. Reported here are results from the combined hydrogen and oxygen isotope analysis aimed at reconstructing relative humidity. Oxygen isotope ratios (δ18O) of biogenic apatite from mammalian tooth enamel and fish scales vary with environment, physiology and diet. Because mammals are homeothermic, they primarily track surface water values with predictable physiological offsets. Hydrogen isotope ratios (δD) of leaf-wax lipids (long-chain n-alkanes) reflect both meteoric water δD values and additional D-enrichment caused by evapotranspiration. The enrichment factor between water δD and n-alkane δD can therefore be used as a proxy for relative humidity (RH). In this study, δ18O of surface water is estimated using the δ18O of Coryphodon tooth enamel. We use these δ18O values to estimate surface water δD values using the Global Meteoric Water Line (δD = 8δ18O + 10). We then calculate relative humidity from n-alkane δD values using a Craig-Gordon type isotopic model for D-enrichment caused by transpiration from leaves. Results of the combined hydrogen-oxygen isotope paleohygrometer indicate a general rise in
Bush, R. T.; McInerney, F. A.; Baczynski, A. A.; Wing, S. L.
2011-12-01
Long chain n-alkanes (C21-C35) are well-known as biomarkers of terrestrial plants. They can be preserved across a wide range of terrestrial and marine environments, survive in the sedimentary record for millions of years, and can serve as proxies for ancient environments. Most n-alkane records are derived from sediments rather than directly from fossil leaves. However, little is known about the fidelity of the n-alkane record: how and where leaf preservation relates to n-alkane preservation and how patterns of n-alkane carbon isotope ratios (δ13C) compare to living relatives. To examine these questions, we analyzed n-alkanes from fluvial sediments and individual leaf fossils collected in the Bighorn Basin, Wyoming, across the Paleocene-Eocene Thermal Maximum (PETM) carbon isotope excursion. We assessed the fidelity of the n-alkane signature from individual fossil leaves via three separate means. 1) Spatial variations were assessed by comparing n-alkane concentrations on a fossil leaf and in sediments both directly adjacent to the leaf and farther away. Absolute concentrations were greater within the compression fossil than in the directly adjacent sediment, which were in turn greater than in more distant sediment. 2) n-Alkane abundances and distributions were examined in fossil leaves having a range of preservational quality, from fossils with intact cuticle to carbonized fossils lacking cuticle and higher-order venation. The best preserved fossils preserved a higher concentration of n-alkanes and showed the most similar n-alkane distribution to living relatives. However, a strong odd over even predominance suggests a relatively unmodified plant source occurred in all samples regardless of preservation state. 3) n-Alkane δ13C values were measured for both fossil leaves and their living relatives. Both the saw-tooth pattern of δ13C values between odd and even chain lengths and the general decrease in δ13C values with increasing chain length are consistent with
Zanchettin, D.; Bothe, O.; Rubino, A.; Jungclaus, J. H.
2016-08-01
We assess internally-generated climate variability expressed by a multi-model ensemble of unperturbed climate simulations. We focus on basin-scale annual-average sea surface temperatures (SSTs) from twenty multicentennial pre-industrial control simulations contributing to the fifth phase of the Coupled Model Intercomparison Project. Ensemble spatial patterns of regional modes of variability and ensemble (cross-)wavelet-based phase-frequency diagrams of corresponding paired indices summarize the ensemble characteristics of inter-basin and regional-to-global SST interactions on a broad range of timescales. Results reveal that tropical and North Pacific SSTs are a source of simulated interannual global SST variability. The North Atlantic-average SST fluctuates in rough co-phase with the global-average SST on multidecadal timescales, which makes it difficult to discern the Atlantic Multidecadal Variability (AMV) signal from the global signal. The two leading modes of tropical and North Pacific SST variability converge towards co-phase in the multi-model ensemble, indicating that the Pacific Decadal Oscillation (PDO) results from a combination of tropical and extra-tropical processes. No robust inter- or multi-decadal inter-basin SST interaction arises from our ensemble analysis between the Pacific and Atlantic oceans, though specific phase-locked fluctuations occur between Pacific and Atlantic modes of SST variability in individual simulations and/or periods within individual simulations. The multidecadal modulation of PDO by the AMV identified in observations appears to be a recurrent but not typical feature of ensemble-simulated internal variability. Understanding the mechanism(s) and circumstances favoring such inter-basin SST phasing and related uncertainties in their simulated representation could help constraining uncertainty in decadal climate predictions.
Djeison Cesar Batista
2011-09-01
Full Text Available Thermal rectification of wood was developed in the decade of 1940 and has been largely studied and produced in Europe. In Brazil, the research about this technique is still little and sparse, but it has gained attention nowadays. The aim of this study was to evaluate the influence of time and temperature of rectification on the reduction of maximum swelling of Eucalyptus grandis wood. According to the results obtained it is possible to achieve reductions of about 50% on the maximum volumetric swelling of Eucalyptus grandis wood. Best results were obtained for 230°C of thermal rectification rather than 200°C. The factor temperature was more significant than time, once that there was no significant difference between the times used (1, 2 and 3 hours. There was no significant interaction between the factors time and temperature.
Toebes, Marcel J P; Hoozemans, Marco J M; Dekker, Joost; van Dieën, Jaap H
2014-01-01
This study assessed effects of unilateral leg muscle fatigue (ULMF) on balance control in gait during the stance and swing phases of the fatigued leg in healthy elderly, to test the assumption that leg muscle strength limits balance control during the stance-phase. Ten subjects (aged 63.4, SD 5.5 years) walked on a treadmill in 4 conditions: unperturbed unfatigued, unperturbed fatigued, perturbed unfatigued, and perturbed fatigued. The perturbations were lateral trunk pulls just before contralateral heel contact. ULMF was evoked by unilateral squat exercise until task failure. Isometric knee extension strength was measured to verify the presence of muscle fatigue. Between-stride standard deviations and Lyapunov exponents of trunk kinematics were used as indicators of balance control. Required perturbation force and the deviation of trunk kinematics from unperturbed gait were used to assess perturbation responses. Knee extension strength decreased considerably (17.3% SD 8.6%) as a result ULMF. ULMF did not affect steady-state gait balance. Less force was required to perturb subjects when the fatigued leg was in the stance-phase compared to the swing-phase. Subjects showed a faster return to the unperturbed gait pattern in the fatigued than in the unfatigued condition, after perturbations in swing and stance of the fatigued leg. The results of this study are not in line with the hypothesized effects of leg muscle fatigue on balance in gait. The healthy elderly subjects were able to cope with substantial ULMF during steady-state gait and demonstrated faster balance recovery after laterally directed mechanical perturbations in the fatigued than in the unfatigued condition.
Petra Hlavackova
Full Text Available The present study was designed to assess the relative contribution of each leg to unperturbed bipedal posture in lower limb amputees. To achieve this goal, eight unilateral traumatic trans-femoral amputees (TFA were asked to stand as still as possible on a plantar pressure data acquisition system with their eyes closed. Four dependent variables were computed to describe the subject's postural behavior: (1 body weight distribution, (2 amplitude, (3 velocity and (4 regularity of centre of foot pressure (CoP trajectories under the amputated (A leg and the non-amputated (NA leg. Results showed a larger body weight distribution applied to the NA leg than to the A leg and a more regular CoP profiles (lower sample entropy values with greater amplitude and velocity under the NA leg than under the A leg. Taken together, these findings suggest that the NA leg and the A leg do not equally contribute to the control of unperturbed bipedal posture in TFA. The observation that TFA do actively control unperturbed bipedal posture with their NA leg could be viewed as an adaptive process to the loss of the lower leg afferents and efferents because of the unilateral lower-limb amputation. From a methodological point of view, these results demonstrate the suitability of computing bilateral CoP trajectories regularity for the assessment of lateralized postural control under pathological conditions.
Jacob N. Chung
2014-01-01
Full Text Available Two concept systems that are based on the thermochemical process of high-temperature steam gasification of lignocellulosic biomass and municipal solid waste are introduced. The primary objectives of the concept systems are 1 to develop the best scientific, engineering, and technology solutions for converting lignocellulosic biomass, as well as agricultural, forest and municipal waste to clean energy (pure hydrogen fuel, and 2 to minimize water consumption and detrimental impacts of energy production on the environment (air pollution and global warming. The production of superheated steam is by hydrogen combustion using recycled hydrogen produced in the first concept system while in the second concept system concentrated solar energy is used for the steam production. A membrane reactor that performs the hydrogen separation and water gas shift reaction is involved in both systems for producing more pure hydrogen and CO2 sequestration. Based on obtaining the maximum hydrogen production rate the hydrogen recycled ratio is around 20% for the hydrogen combustion steam heating system. Combined with pure hydrogen production, both high temperature steam gasification systems potentially possess more than 80% in first law overall system thermodynamic efficiencies.
Electron diffusion in a sheared unperturbed magnetic field and an electrostatic stochastic field
Petrisor, I [Department of Physics, Association Euratom-MEdC, Romania, University of Craiova, 13 A I Cuza Str., 200585 Craiova (Romania); Negrea, M [Department of Physics, Association Euratom-MEdC, Romania, University of Craiova, 13 A I Cuza Str., 200585 Craiova (Romania); Weyssow, B [Physique Statistique-Plasmas, Association Euratom-Etat Belge, Universite Libre de Bruxelles, Campus Plaine, Bd. du Triomphe, 1050 Brussels (Belgium)
2007-01-15
The electron diffusion induced by a two-dimensional electrostatic turbulence, in a sheared slab approximation of the toroidal magnetic geometry, is studied firstly using the decorrelation trajectory method (DCT), secondly by direct numerical simulation. The former semi-analytical method allows us to go beyond the Corrsin approximation, thus allowing for a non-classical analysis of the particle trapping phenomenon. The DCT results are compared to the transport properties of the electrons obtained by numerical simulations assuming an isotropic spectrum of electrostatic drift type turbulence that is Gaussian for small wavevectors and power-law k{sup -3} for large wavevectors. The 'radial' and the 'poloidal' running and asymptotic diffusion coefficients of thermal electrons are obtained for physically relevant parameter values. The existence of enhanced diffusion in the poloidal direction is observed in the presence of magnetic shear. The agreement between the semi-analytical method and the purely numerical method is pointed out.
Makarova, Maria; Wright, James D.; Miller, Kenneth G.; Babila, Tali L.; Rosenthal, Yair; Park, Jill I.
2017-01-01
We present new δ13C and δ18O records of surface (Morozovella and Acarinina) and thermocline dwelling (Subbotina) planktonic foraminifera and benthic foraminifera (Gavelinella, Cibicidoides, and Anomalinoides) during the Paleocene-Eocene Thermal Maximum (PETM) from Millville, New Jersey, and compare them with three other sites located along a paleoshelf transect from the U.S. mid-Atlantic coastal plain. Our analyses show different isotopic responses during the PETM in surface versus thermocline and benthic species. Whereas all taxa record a 3.6-4.0‰ δ13C decrease associated with the carbon isotope excursion, thermocline dwellers and benthic foraminifera show larger δ18O decreases compared to surface dwellers. We consider two scenarios that can explain the observed isotopic records: (1) a change in the water column structure and (2) a change in habitat or calcification season of the surface dwellers due to environmental stress (e.g., warming, ocean acidification, surface freshening, and/or eutrophication). In the first scenario, persistent warming during the PETM would have propagated heat into deeper layers and created a more homogenous water column with a thicker warm mixed layer and deeper, more gradual thermocline. We attribute the hydrographic change to decreased meridional thermal gradients, consistent with models that predict polar amplification. The second scenario assumes that environmental change was greater in the mixed layer forcing surface dwellers to descend into thermocline waters as a refuge or restrict their calcification to the colder seasons. Although both scenarios are plausible, similar δ13C responses recorded in surface, thermocline, and benthic foraminifera challenge mixed layer taxa migration.
Lavrushin, Yu. A.; Spiridonova, E. A.; Engovatova, A. V.
2016-11-01
The succession of short-term natural events at the thermal humid maximum in the Middle Ages (10th-12th centuries) within the forest zones of European Russia was established. The archaeological excavation in the most ancient part of the town of Yaroslavl opened a thick cultural horizon, where fragments of lacustrine deposits dating back to the 11th-12th centuries were preserved. The most ancient fragments of the construction, found in lacustrine deposits, date back to the first third of the 13th century. An analysis of the structural and textural peculiarities of these deposits made it possible to reconstruct types of hydrogeological regime in the Timerevo paleolake and a paleostrait between this paleolake and Lake Nero. Thus, the waterway between the central part of the Principality of Rostov and early Yaroslavl (the first Russian settlement at the Great Volga Waterway) was revealed. The probable reasons for a rapid warming event followed by a cooling one in the Middle Ages are discussed.
Blaschek, M.; Renssen, H.
2012-04-01
In the early-to-mid Holocene a period of relatively warm climate, known as the Holocene thermal maximum (HTM, 11-5 kyr BP), has been associated with the orbitally-forced northern hemisphere summer insolation maximum at approximately 10 kyr BP. Although the HTM is orbitally forced, the spatial and temporal response of its climate signature is diverse. At 9 kyr BP remnants of glacial ice sheets, most importantly the Laurentide Ice Sheet (LIS), modified the climate of the North Atlantic region by freshening the ocean surface through melt water discharge, and by altering the surface albedo and topography. A previous climate modelling study (Renssen et al. 2009) has shown that the LIS delayed the HTM in the Nordic Seas by up to 3000 years. We extend this approach by introducing another source of melt water in the early Holocene, the Greenland Ice Sheet (GIS). The GIS was likely up to 25% larger (at 9 kyr BP) in volume than at present-day (Vinther et al. 2009, Peltier, 2004) and is therefore potentially an important regional contributor to climate change in the Nordic Seas. We present here simulations performed with the LOVECLIM1.2 global ocean-atmosphere-vegetation model. These simulations seek to highlight the spatial and temporal impact of GIS melting on the early Holocene climate, in terms of sea surface temperature (SST). Several sensitivity experiments with fixed 9 kyr BP forcings were performed for different Greenland melt water fluxes to test model and climate sensitivity. These melt water fluxes range from 0 to 52 mSv. The sensitivity experiments show that GIS melting considerably influences sea surface conditions around the southern part of Greenland, and that 13 to 26 mSv of GIS melting, in a combination with the LIS background melting, agrees better in that region with proxy-based SST reconstructions. In a further step, transient simulations exhibit the long term (9 to 0 kyr BP) impact of GIS melting on the development of the Holocene climate. Transient
Robinson, Oliver J; Bond, Rebecca L; Roiser, Jonathan P
2015-01-01
Anxiety and stress-related disorders constitute a large global health burden, but are still poorly understood. Prior work has demonstrated clear impacts of stress upon basic cognitive function: biasing attention toward unexpected and potentially threatening information and instantiating a negative affective bias. However, the impact that these changes have on higher-order, executive, decision-making processes is unclear. In this study, we examined the impact of a translational within-subjects stress induction (threat of unpredictable shock) on two well-established executive decision-making biases: the framing effect (N = 83), and temporal discounting (N = 36). In both studies, we demonstrate (a) clear subjective effects of stress, and (b) clear executive decision-making biases but (c) no impact of stress on these decision-making biases. Indeed, Bayes factor analyses confirmed substantial preference for decision-making models that did not include stress. We posit that while stress may induce subjective mood change and alter low-level perceptual and action processes (Robinson et al., 2013c), some higher-level executive processes remain unperturbed by these impacts. As such, although stress can induce a transient affective biases and altered mood, these need not result in poor financial decision-making.
Oliver Joe Robinson
2015-08-01
Full Text Available Anxiety and stress-related disorders constitute a large global health burden, but are still poorly understood. Prior work has demonstrated clear impacts of stress upon basic cognitive function: biasing attention towards unexpected and potentially threatening information and instantiating a negative affective bias. However, the impact that these changes have on higher-order, executive, decision-making processes is unclear. In this study we examined the impact of a translational within-subjects stress induction (threat of unpredictable shock on two well-established executive decision-making biases: the framing effect (N=83, and temporal discounting (N=36. In both studies, we demonstrate a clear subjective effects of stress, and b clear executive decision-making biases but c no impact of stress on these decision-making biases. Indeed, Bayes factor analyses confirmed substantial preference for decision-making models that did not include stress. We posit that while stress may induce subjective mood change and alter low-level perceptual and action processes (Robinson et al., 2013b, some higher-level executive processes remain unperturbed by these impacts. As such, although stress can induce a transient affective biases and altered mood, these need not result in poor financial decision-making.
Cui, Y.; Kump, L.; Ridgwell, A.; Junium, C.; Diefendorf, A. F.; Freeman, K. H.; Urban, N.
2010-12-01
Newly analyzed core material from Svalbard presents the most expanded sedimentary section spanning the Paleocene Eocene Thermal Maximum (PETM) studied to date. Carbon isotopic analysis of the bulk organic matter extracted from core BH9-05 details the onset of the negative carbon isotope excursion (CIE) of approximately 4.2‰ over 19,000 years (8 m of section, sampled every 30 cm) and its recovery over 50 m of section, representing 150,000 years. The CIE of terrestrial higher plant n-alkanes (~6‰) is larger than that of the bulk organic carbon (4.2‰), suggesting the CIE of the atmospheric CO2 is in the range of 4.2 to 6‰. We use a novel approach to modeling the excursion, forcing an Earth system model of intermediate complexity to conform to the total organic carbon isotope record, yielding rates of carbon release at the PETM for a specified isotopic composition representing end-member potential sources (methane or fossil organic matter). We find that the peak rate of carbon addition is only a small fraction of the current rate of fossil fuel burning (9 Pg C/yr) whether the source is methane (0.3 Pg C/yr; δ13C = -60‰) or organic matter (1.7 Pg C/yr; δ13C = -22‰). Model/data comparison, especially the observed and modeled seafloor carbonate dissolution record, favors the higher peak rate and larger (~13,000 Pg C) cumulative addition associated with an organic-matter source, such as rapid oxidation of peat/coal/marine organic matter, thermal alteration of marine organic matter during emplacement of the N. Atlantic Volcanic Province, or a mix of relatively 13C enriched (volcanic) and relatively 13C depleted (methane) sources. However, model sensitivity analysis shows that while the rate and amount of carbon added (for a specified source type) is relatively insensitive to key model uncertainties, the predicted seafloor carbonate dissolution response is quite sensitive to the presumed initial ocean alkalinity and seafloor carbonate distribution (i.e., the
Kinkhabwala, Ali
2013-01-01
The most fundamental problem in statistics is the inference of an unknown probability distribution from a finite number of samples. For a specific observed data set, answers to the following questions would be desirable: (1) Estimation: Which candidate distribution provides the best fit to the observed data?, (2) Goodness-of-fit: How concordant is this distribution with the observed data?, and (3) Uncertainty: How concordant are other candidate distributions with the observed data? A simple unified approach for univariate data that addresses these traditionally distinct statistical notions is presented called "maximum fidelity". Maximum fidelity is a strict frequentist approach that is fundamentally based on model concordance with the observed data. The fidelity statistic is a general information measure based on the coordinate-independent cumulative distribution and critical yet previously neglected symmetry considerations. An approximation for the null distribution of the fidelity allows its direct conversi...
A. Sluijs
2009-08-01
Full Text Available Late Paleocene and Early Eocene climates and ecosystems underwent significant change during several transient global warming phases, associated with rapidly increasing atmospheric carbon concentrations, of which the Paleocene-Eocene Thermal Maximum (PETM; ~55.5 Ma is best studied. While biotic response to the PETM as a whole (~170 kyrs has been relatively well documented, variations during the PETM have been neglected. Here we present organic dinoflagellate cyst (dinocyst distribution patterns across two stratigraphically expanded PETM sections from the New Jersey Shelf, Bass River and Wilson Lake. Many previously studied sites show a uniform abundance of the thermophilic and presumably heterotrophic taxon Apectodinium that spans the entire carbon isotope excursion (CIE of the PETM. In contrast, the New Jersey sections show large variations in abundances of many taxa during the PETM, including the new species Florentinia reichartii that we formally propose. We infer paleoecological preferences of taxa that show temporal abundance peaks, both qualitative and absolute quantitative, from empirical as well as statistical information, i.e., principle (PCA and canonical correspondence analyses (CCA. In the CCAs, we combine the dinocyst data with previously published environmental proxy data from these locations, such as TEX_{86} paleothermometry, magnetic susceptibility and sedimentary size fraction. The combined information supports previous inferences that sea level rose during the PETM, but also indicates a (regional increase in fresh-water runoff that started ~10 kyr after the onset of the CIE, and perhaps precession-paced cycles in sea surface productivity. The highly variable dinocyst assemblages of the PETM contrast with rather stable Upper Paleocene assemblages, which suggests that carbon input caused a dynamic climate state, at least regionally.
Harrington, G.; Jardine, P.
2012-12-01
The early Palaeogene hyperthermals provide an unprecedented opportunity to investigate the biotic responses to rapid and transient global warming events. As part of the Bighorn Basin Coring Project (BBCP), we have analyzed 182 sporomorph (pollen and spore) samples from three newly cored sites in the Bighorn Basin of Wyoming. Two sites, Basin Substation (121 samples) and Polecat Bench (41 samples), contain the Paleocene-Eocene Thermal Maximum (PETM, ETM1), and one early Eocene site, Gilmore Hill (20 samples), contains the ELMO (ETM2) event. We have focused initially on the Basin Substation section, because it is more organic rich, has demonstrated higher sporomorph recovery potential than the other two sites, and is the main focus of complementary geochemical analyses. Below 90 m core depth sporomorph concentrations are typically 1000 - 10 000 grains/gram, but between 90 and 60 m these decline to gymnosperms Cupressacites hiatipites (cypress, Cupressaceae) and bisaccate pollen (Pinaceae and/or Podocarpaceae), and the angiosperm taxa Polyatriopollenites vermontensis (wingnut or wheel wingnut, Juglandaceae), Caryapollenites spp. (hickory, Juglandaceae), and Alnipollenites spp. (alder, Betulaceae). However, samples are heterogeneous in terms of the dominant taxon, with different taxa having the highest relative abundance in different samples. In the upper part of the core, the assemblage is similar to that in the lower part, but with a more consistent dominance of gymnosperm taxa, and with the addition of Eocene marker taxa Intratriporopollenites instructus (linden, Tilioideae) and Celtis spp. (hackberry, Cannabaceae). These both have their first appearance at 56.14 m in the core, just above the zone of low sporomorph recovery. These results point to (a) a decrease in sporomorph preservation that is linked to environmental change during the PETM event, and (b) repeated reorganizations of plant relative abundances prior to the PETM. Current research is focusing on the
Fricke, Henry C.; Clyde, William C.; O'Neil, James R.; Gingerich, Philip D.
1998-07-01
Oxygen isotope records of Cenozoic sea water temperatures indicate that a rapid warming event known as the Latest Paleocene Thermal Maximum (LPTM) occurred during the otherwise gradual increase in world temperatures during the Late Paleocene and Early Eocene. Oxygen isotope analysis of the carbonate and phosphate components of hydroxyapatite found in mammalian tooth enamel and body scales of river-dwelling fish from the Bighorn Basin in Wyoming were made to investigate corresponding changes in the terrestrial climate. A comparison of carbonate and phosphate isotope data from modern and fossil material indicates that some diagenetic alteration of the fossil material has occurred, although systematically larger intra-tooth ranges in the oxygen isotope composition of carbonate indicate that it is more likely to have been affected than phosphate. Carbonate and phosphate from the ecologically diverse mammals and fishes both record a shift to higher oxygen isotope ratios at the same time and of the same duration as the LPTM. These shifts reflect a change in the isotopic composition of regional precipitation, which in turn provides the first evidence for continental climate change during the LPTM. Assuming the present-day relation between the oxygen isotope composition of precipitation and temperature applies to conditions in the past, and that animal physiology and behavior is relatively invariant over time, the isotopic shift is equivalent to an increase of surface temperature in western North America of several degrees. This result is consistent with the magnitude of high-latitude ocean warming, and provides a basis for relating marine and terrestrial oxygen isotope records to records of terrestrial biotic change.
Chen, Zuoling; Wang, Xu; Hu, Jianfang; Yang, Shiling; Zhu, Min; Dong, Xinxin; Tang, Zihua; Peng, Ping'an; Ding, Zhongli
2014-12-01
The carbon isotope excursion (CIE) associated with the Paleocene-Eocene Thermal Maximum (PETM) has been recognized for the first time in the micritic carbonate, total organic carbon (TOC) and black carbon (BC) contained within the lacustrine sediments from the Nanyang Basin, central China. The remarkably large excursion (∼ - 6 ‰) in the δ13CTOC and δ13CBC values is possibly attributable to increased humidity and elevated pCO2 concentration. The ∼ - 4 ‰ CIE recorded in the δ13Ccalcite, reflecting the average isotope change of the watershed system, is consistent with that observed in planktonic foraminifera. This correspondence suggests that the true magnitude of the carbon isotope excursion in the ocean-atmosphere system is likely close to - 4 ‰. The ∼10 m excursion onset in our multi-proxy δ13C records demonstrates that the large input of 13C-depleted carbon into the ocean-atmosphere system was not geologically instantaneous. Despite difference and somewhat smoothness in detailed pattern of the CIE due to localized controls on different substrates, inorganic and organic δ13C data generally depict a gradual excursion onset at least over timescales of thousands of years. In addition, continental temperature reconstruction, based on the distribution of membrane lipids of bacteria, suggests a warming of ∼4 °C prior to the PETM and ∼7 °C increase in temperature during the PETM. The temperature data are overall similar in pattern and trend to the δ13C change across the PETM. These observations, combined with pre-CIE warming, are in line with the idea that 13C-depleted carbon release operated as a positive feedback to temperature, suggesting supply from one or more large organic carbon reservoirs on Earth's surface.
van der Meulen, Bas; Abels, Hemmo; Meijer, Niels; Gingerich, Philip; Lourens, Lucas
2016-04-01
The addition of major amounts of carbon to the exogenic carbon pool caused rapid climate change and faunal turnover during the Paleocene-Eocene Thermal Maximum (PETM) around 56 million years ago. Constraints are still needed on the duration of the onset, main body, and recovery of the event. The Bighorn Basin in Wyoming provides expanded terrestrial sections spanning the PETM and lacking the carbonate dissolution present in many marine records. Here we provide new carbon isotope records for the Polecat Bench and Head of Big Sand Coulee sections, two parallel sites in the northern Bighorn Basin, at unprecedented resolution. Cyclostratigraphic analysis of these fluvial sediment records using descriptive sedimentology and proxy records allows subdivision into intervals dominated by avulsion deposits and intervals dominated by overbank deposits. These sedimentary sequences alternate in a regular fashion and are related to climatic precession. Correlation of the two, 8-km-spaced sections shows that the avulsion-overbank cycles are laterally consistent. The presence of longer-period alternations, related to modulation by the 100-kyr eccentricity cycle, corroborates the precession influence on the sediments. Sedimentary cyclicity is then used to develop a floating precession-scale age model for the PETM carbon isotope excursion (CIE). We find a CIE body encompassing 95 kyrs aligning with marine cyclostratigraphic age models. The duration of the CIE onset is estimated at 5 kyrs, but difficult to determine because sedimentation rates vary at the sub-precession scale. The CIE recovery starts with a 2 to 4 per mille step and lasts 40 or 90 kyrs, depending on what is considered the carbon isotope background state.
Denis, E. H.; Foreman, B.; Maibauer, B.; Bowen, G. J.; Collinson, M. E.; Belcher, C.; Freeman, K. H.
2014-12-01
Projections for Earth's future suggest that wildfire activity will increase with global warming, but the factors controlling fire are complex. The Paleocene-Eocene Thermal Maximum (PETM) was a geologically abrupt global warming event that had profound effects on vegetation and hydrologic patterns and serves as an analog for modern climate change. Carbon burn-down (i.e., oxidation of organic matter) could amplify feedbacks with warming through release of carbon to the atmosphere. To assess relationships between climate, fire and soil respiration, we evaluated biomarkers, including polycyclic aromatic hydrocarbons (PAHs), charcoal and total organic carbon (TOC) for three paleo-floodplain depositional sites in the Western USA. Samples were selected from Bighorn Basin Coring Project cores in the Bighorn Basin, Wyoming (at Basin Substation and Polecat Bench) and from an outcrop section in the Piceance Basin, Colorado. In general, the Paleocene had higher PAH concentrations (μg/g TOC) than the Eocene, but there was no clear trend during the onset (~20 kyr) or through the PETM (~200 kyr). Median %TOC decreased through the PETM, then increased in the Eocene, but did not return to Paleocene values. At Basin Substation, PAH concentrations decreased by an order of magnitude during the PETM interval, concurrent with a decline in TOC and charcoal. High molecular weight (MW) PAHs tend to dominate, especially in low TOC samples; this suggests preferential loss of low MW PAHs, which are relatively more susceptible to post-depositional processes. Lithology, TOC and the relative proportion of PAHs help discern the signals of carbon oxidation, by fire and by soil respiration. Despite climate conditions that tend to promote fire, there is no evidence for increased fires at the onset or throughout the PETM. Biomarker and petrographic data suggest decreased organic carbon preservation, including loss of refractory carbon, at Basin Substation during the PETM. This suggests soil carbon
Moossen, H. M.; Abell, R.; Quillmann, U.; Andrews, J. T.; Bendle, J. A.
2011-12-01
Holocene climate change is of significantly smaller amplitude than the Pleistocene Glacial-Interglacial cycles, but climatic variations have affected humans over at least the last 4000 years. Studying Holocene climate variations is important to disentangle climate change caused by anthropogenic influences from natural climate change. Sedimentary records stemming from fjords afford the opportunity to study marine and terrestrial paleo-climatic changes and linking the two together. Typically high sediment accumulation rates of fjordic environments facilitate resolution of rapid climate change (RCC) events. The fjords of Northwest Iceland are ideal for studying Holocene climate change as they receive warm water from the Irminger current, but are also influenced by the east Greenland current which brings polar waters to the region (Jennings et al., 2011). In the Holocene, Nordic Seas and the Arctic have been sensitive to climate change. The 8.2 ka event, a cool interval, highlights the sensitivity of that region. Recent climate variations such as the Little Ice Age have been detected in sedimentary records around Iceland (Sicre et al., 2008). We reconstruct Holocene marine and terrestrial climate change producing high resolution (1sample/ 30 years) records from 10700 cal a BP to 300 cal a BP using biomarkers. Alkenones, terrestrial leaf wax components, GDGTs and C/N ratios from a sediment core (MD99-2266) from the mouth of the Ìsafjardardjúp fjord were studied. For more information on the core and evolution of the fjord during the Holocene consult Quillmann et al., (2010) The average chain length (ACL) of terrestrial n-alkanes indicates changes in aridity, and the alkenone unsaturation index represents changes in sea surface temperature. These independent records exhibit similar trends over the studied time period. Our alkenone derived SST record shows the Holocene Thermal Maximum, Holocene Neoglaciation as well as climate change associated with the Medieval Warm
Sluijs, A.; van Roij, L.; Harrington, G. J.; Schouten, S.; Sessa, J. A.; LeVay, L. J.; Reichart, G.-J.; Slomp, C. P.
2014-07-01
The Paleocene-Eocene Thermal Maximum (PETM, ~ 56 Ma) was a ~ 200 kyr episode of global warming, associated with massive injections of 13C-depleted carbon into the ocean-atmosphere system. Although climate change during the PETM is relatively well constrained, effects on marine oxygen concentrations and nutrient cycling remain largely unclear. We identify the PETM in a sediment core from the US margin of the Gulf of Mexico. Biomarker-based paleotemperature proxies (methylation of branched tetraether-cyclization of branched tetraether (MBT-CBT) and TEX86) indicate that continental air and sea surface temperatures warmed from 27-29 to ~ 35 °C, although variations in the relative abundances of terrestrial and marine biomarkers may have influenced these estimates. Vegetation changes, as recorded from pollen assemblages, support this warming. The PETM is bracketed by two unconformities. It overlies Paleocene silt- and mudstones and is rich in angular (thus in situ produced; autochthonous) glauconite grains, which indicate sedimentary condensation. A drop in the relative abundance of terrestrial organic matter and changes in the dinoflagellate cyst assemblages suggest that rising sea level shifted the deposition of terrigenous material landward. This is consistent with previous findings of eustatic sea level rise during the PETM. Regionally, the attribution of the glauconite-rich unit to the PETM implicates the dating of a primate fossil, argued to represent the oldest North American specimen on record. The biomarker isorenieratene within the PETM indicates that euxinic photic zone conditions developed, likely seasonally, along the Gulf Coastal Plain. A global data compilation indicates that O2 concentrations dropped in all ocean basins in response to warming, hydrological change, and carbon cycle feedbacks. This culminated in (seasonal) anoxia along many continental margins, analogous to modern trends. Seafloor deoxygenation and widespread (seasonal) anoxia likely
Schulte, P.; Scheibner, C.; Speijer, R. P.
2009-04-01
In the Dababiya Quarry section, the Paleocene-Eocene Thermal Maximum (PETM) consists of a succession of five characteristic beds that can be traced throughout eastern Egypt. The base of these beds defines the Global boundary Stratotype Section and and Point (GSSP) of the Eocene. Previous studies of mineralogical and geochemical proxies have suggested a period of euxinic conditions from the onset of the PETM up to the beginning of the recovery phase (Aubry et al., 2007). Dupuis et al. (2003) described prominent mineralogical changes (increase of illite and chlorite-smectite mixed layers) that occurred contemporaneous to the maximum negative carbon isotope values. A sea-level fall immediately preceding the onset of the PETM, followed by a sea-level rise and enhanced upwelling during the PETM is postulated in Egypt (Speijer and Wagner, 2002). However, a detailed study of the Dababiya Quarry beds, and specifically their element geochemistry, is currently lacking. Therefore, we investigated the Dababiya Quarry section by X-ray diffractometry (XRD; bulk rock and clay mineralogy) as well as by X-ray fluorescence analysis (XRF; major and trace elements and rare earth elements, REE) to detail the succession of environmental events during the PETM. (i) The absence of carbonate (as low as event bed 1 indicates severe carbonate dissolution. A sharp short-lived increase in siliciclastic detritus (PETM) as well as an increase of chlorite and illite as well as well-crystallized smectite suggest deposition during low sea-level and increased weathering rates. Event bed 1 is also strongly deprived in REEs and shows high Zr/Rb ratios, indicative for input of coarse siliciclastic detritus. (ii) Subsequently, during the peak phase of the PETM, i.e. during the maximum negative shift of the Carbon Isotope Excursion ("CIE"), a short-lived period of pronounced anoxic sedimentary conditions is indicated by sediment lamination, absence of benthic life, elevated TOC, trace metal enrichment
古新世-始新世极热事件研究进展%A REVIEW ON THE PALEOCENE-EOCENE THERMAL MAXIMUM
陈祚伶; 丁仲礼
2011-01-01
The Paleocene-Eocene Thermal Maximum ( PETM) is an extreme carbon perturbation and global warming event,which was superimposed on the long-term Early Cenozoic warming trend. The PETM is characterized by an abrupt and large negative excursion ( - 2‰ ~ - 6‰) of carbon isotope compositions of marine and terrestrial sedimentary materials. Paleotemperature proxies suggest an increase in global surface temperature of approximately 5 ~6℃ ,and a coincident decrease in temperature gradient between high-latitudes and low-latitudes. This event is correlative with a global accelerated hydrological cycle and large-scale biotic turnover and vertebrate mammalian migrations. Based on carbon isotope records and computer simulations, the amount of carbon totally released to the exogenic carbon cycle system is estimated to be comparable with the anticipative carbon amount that would be released to the atmosphere by burns of fossil fuels. Therefore, a comprehensive study of this event is potentially helpful to the projection of the environmental and ecological impacts induced by human activity in the future. In this paper, we overviewed the recent progresses of studies on the event, particularly focusing on the triggering mechanisms, estimation of released total carbon, and the climatic and ecological impacts.Of all mechanisms put forward, large-scale dissociation of methane hydrate is the reliable hypothesis. It is likely that increased temperature before PETM event led to hydrate instability and thus to an enhanced emission of methane, imposing a strong positive feedback that would made dissociation of more methane hydrate along continental slope, and then caused the PETM event. Because of pervasive dissolution of deep sea sedimentary carbonate and severe acidification of ocean, the real magnitude of carbon isotope excursion may be embodied in terrestrial carbon isotope records(ca. -6‰)rather than the ocean archives(ca. -2. 5%o).The -6‰ of CIE(carbon isotope excursion
Barclay, R. S.; Wing, S. L.
2013-12-01
The Paleocene-Eocene Thermal Maximum (PETM) was a geologically brief interval of intense global warming 56 million years ago. It is arguably the best geological analog for a worst-case scenario of anthropogenic carbon emissions. The PETM is marked by a ~4-6‰ negative carbon isotope excursion (CIE) and extensive marine carbonate dissolution, which together are powerful evidence for a massive addition of carbon to the oceans and atmosphere. In spite of broad agreement that the PETM reflects a large carbon cycle perturbation, atmospheric concentrations of CO2 (pCO2) during the event are not well constrained. The goal of this study is to produce a high resolution reconstruction of pCO2 using stomatal frequency proxies (both stomatal index and stomatal density) before, during, and after the PETM. These proxies rely upon a genetically controlled mechanism whereby plants decrease the proportion of gas-exchange pores (stomata) in response to increased pCO2. Terrestrial sections in the Bighorn Basin, Wyoming, contain macrofossil plants with cuticle immediately bracketing the PETM, as well as dispersed plant cuticle from within the body of the CIE. These fossils allow for the first stomatal-based reconstruction of pCO2 near the Paleocene-Eocene boundary; we also use them to determine the relative timing of pCO2 change in relation to the CIE that defines the PETM. Preliminary results come from macrofossil specimens of Ginkgo adiantoides, collected from an ~200ka interval prior to the onset of the CIE (~230-30ka before), and just after the 'recovery interval' of the CIE. Stomatal index values decreased by 37% within an ~70ka time interval at least 100ka prior to the onset of the CIE. The decrease in stomatal index is interpreted as a significant increase in pCO2, and has a magnitude equivalent to the entire range of stomatal index adjustment observed in modern Ginkgo biloba during the anthropogenic CO2 rise during the last 150 years. The inferred CO2 increase prior to the
Basse, Britta; Ubezio, Paolo
2007-07-01
We develop a general mathematical model for a population of cells differentiated by their position within the cell division cycle. A system of partial differential equations governs the kinetics of cell densities in certain phases of the cell division cycle dependent on time t (hours) and an age-like variable tau (hours) describing the time since arrival in a particular phase of the cell division cycle. Transition rate functions control the transfer of cells between phases. We first obtain a theoretical solution on the infinite domain -infinity course, these age distributions are unknown. All is not lost, however, because a cell line before treatment usually lies in a state of asynchronous balanced growth where the proportion of cells in each phase of the cell cycle remain constant. We assume that an unperturbed cell line has four distinct phases and that the rate of transition between phases is constant within a short period of observation ('short' relative to the whole history of the tumour growth) and we show that under certain conditions, this is equivalent to exponential growth or decline. We can then gain expressions for the age distributions. So, in short, our approach is to assume that we have an unperturbed cell line on t
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from...
D. Evans
2015-07-01
Full Text Available Much of our knowledge of past ocean temperatures comes from the foraminifera Mg / Ca palaeothermometer. Several non-thermal controls on foraminifera Mg incorporation have been identified, of which vital-effects, salinity and secular variation in seawater Mg / Ca are the most commonly considered. Ocean carbonate chemistry is also known to influence Mg / Ca, yet this is rarely considered as a source of uncertainty either because (1 precise pH and [CO32−] reconstructions are sparse, or (2 it is not clear from existing culture studies how a correction should be applied. We present new culture data of the relationship between carbonate chemistry for the surface-dwelling planktic species Globigerinoides ruber, and compare our results to data compiled from existing studies. We find a coherent relationship between Mg / Ca and the carbonate system and argue that pH rather than [CO32−] is likely to be the dominant control. Applying these new calibrations to datasets for the Paleocene–Eocene Thermal Maximum (PETM and Eocene–Oligocene Transition (EOT enable us to produce a more accurate picture of surface hydrology change for the former, and a reassessment of the amount of subtropical precursor cooling for the latter. We show that properly corrected Mg / Ca and δ18O datasets for the PETM imply no salinity change, and that the amount of precursor cooling over the EOT has been previously underestimated by ∼ 2 °C based on Mg / Ca. Finally, we present new laser-ablation data of EOT-age Turborotalia ampliapertura from St Stephens Quarry (Alabama, for which a solution ICPMS Mg / Ca record is available (Wade et al., 2012. We show that the two datasets are in excellent agreement, demonstrating that fossil solution and laser-ablation data may be directly comparable. Together with an advancing understanding of the effect of Mg / Casw, the coherent picture of the relationship between Mg / Ca and pH that we outline here represents a step towards producing
Reinhardt, Lutz; von Gosen, Werner; Piepjohn, Karsten; Lückge, Andreas; Schmitz, Mark
2017-04-01
The Stenkul Fiord section on southern Ellesmere Island reveals largely fluvial clastic sediments with intercalated coal seams of the Margaret Formation of Late Paleocene/Early Eocene age according to palynology and vertebrate remains. Field studies in recent years and interpretative mapping of a high-resolution satellite image of the area southeast of Stenkul Fiord revealed that the clastic deposits consist of at least four sedimentary units (Units 1 to 4) separated by unconformities. Several centimeter-thin volcanic ash layers, recognized within coal layers and preserved as crandallite group minerals (Ca-bearing goyazite), suggest an intense volcanic ash fall activity. Based on new U-Pb zircon ages (ID-TIMS) of three ash layers, the volcanic ash fall took place at 53.7 Ma in the Early Eocene, i.e. within the Eocene Thermal Maximum 2 (ETM-2) hyperthermal. The ETM-2 is bracketed further by discrete negative excursions of carbon isotope records of both bulk coal and amber droplets collected from individual coal layers of the section. The identification of the ETM-2 hyperthermal provides a stratigraphic tie-point in the terrestrial Margaret Formation sediments enabling assignment of the lowermost sedimentary Unit 1 to the Late Paleocene-earliest Eocene, Unit 2 to the Early Eocene, whereas Unit 3 and 4 might be Early to Middle Eocene in age. Thus the timing of syn-sedimentary movements of the Eurekan deformation causal for the observed unconformities in the section can be studied and the positions of further hyperthermals like the PETM or the ETM-3 in the section can be identified in the future. The integration of structural studies, new U-Pb zircon ages, and different carbon isotope records provides a new stratigraphic framework for further examination of the unique Early Eocene flora and fauna preserved in this high-latitude outcrop.
Kethireddy, V; Oey, I; Jowett, Tim; Bremer, P
2016-09-16
Sub-lethal injury within a microbial population, due to processing treatments or environmental stress, is often assessed as the difference in the number of cells recovered on non-selective media compared to numbers recovered on a "selective media" containing a predetermined maximum non-inhibitory concentration (MNIC) of a selective agent. However, as knowledge of cell metabolic response to injury, population diversity and dynamics increased, the rationale behind the conventional approach of quantifying sub-lethal injury must be scrutinized further. This study reassessed the methodology used to quantify sub-lethal injury for Saccharomyces cerevisiae cells (≈ 4.75 Log CFU/mL) exposed to either a mild thermal (45°C for 0, 10 and 20min) or a mild pulsed electric field treatment (field strengths of 8.0-9.0kV/cm and energy levels of 8, 14 and 21kJ/kg). Treated cells were plated onto either Yeast Malt agar (YM) or YM containing NaCl, as a selective agent at 5-15% in 1% increments. The impact of sub-lethal stress due to initial processing, the stress due to selective agents in the plating media, and the subsequent variation of inhibition following the treatments was assessed based on the CFU count (cell numbers). ANOVA and a generalised least squares model indicated significant effects of media, treatments, and their interaction effects (P<0.05) on cell numbers. It was shown that the concentration of the selective agent used dictated the extent of sub-lethal injury recorded owing to the interaction effects of the selective component (NaCl) in the recovery media. Our findings highlight a potential common misunderstanding on how culture conditions impact on sub-lethal injury. Interestingly for S. cerevisiae cells the number of cells recovered at different NaCl concentrations in the media appears to provide valuable information about the mode of injury, the comparative efficacy of different processing regimes and the inherent degree of resistance within a population. This
Evans, David; Wade, Bridget S.; Henehan, Michael; Erez, Jonathan; Müller, Wolfgang
2016-04-01
Much of our knowledge of past ocean temperatures comes from the foraminifera Mg / Ca palaeothermometer. Several nonthermal controls on foraminifera Mg incorporation have been identified, of which vital effects, salinity, and secular variation in seawater Mg / Ca are the most commonly considered. Ocean carbonate chemistry is also known to influence Mg / Ca, yet this is rarely examined as a source of uncertainty, either because (1) precise pH and [CO32-] reconstructions are sparse or (2) it is not clear from existing culture studies how a correction should be applied. We present new culture data of the relationship between carbonate chemistry and Mg / Ca for the surface-dwelling planktic species Globigerinoides ruber and compare our results to data compiled from existing studies. We find a coherent relationship between Mg / Ca and the carbonate system and argue that pH rather than [CO32-] is likely to be the dominant control. Applying these new calibrations to data sets for the Paleocene-Eocene Thermal Maximum (PETM) and Eocene-Oligocene transition (EOT) enables us to produce a more accurate picture of surface hydrology change for the former and a reassessment of the amount of subtropical precursor cooling for the latter. We show that pH-adjusted Mg / Ca and δ18O data sets for the PETM are within error of no salinity change and that the amount of precursor cooling over the EOT has been previously underestimated by ˜ 2 °C based on Mg / Ca. Finally, we present new laser-ablation data of EOT-age Turborotalia ampliapertura from St. Stephens Quarry (Alabama), for which a solution inductively coupled plasma mass spectrometry (ICPMS) Mg / Ca record is available (Wade et al., 2012). We show that the two data sets are in excellent agreement, demonstrating that fossil solution and laser-ablation data may be directly comparable. Together with an advancing understanding of the effect of Mg / Casw, the coherent picture of the relationship between Mg / Ca and pH that we outline
Maximum Autocorrelation Factorial Kriging
Nielsen, Allan Aasbjerg; Conradsen, Knut; Pedersen, John L.; Steenfelt, Agnete
2000-01-01
This paper describes maximum autocorrelation factor (MAF) analysis, maximum autocorrelation factorial kriging, and its application to irregularly sampled stream sediment geochemical data from South Greenland. Kriged MAF images are compared with kriged images of varimax rotated factors from an ordinary non-spatial factor analysis, and they are interpreted in a geological context. It is demonstrated that MAF analysis contrary to ordinary non-spatial factor analysis gives an objective discrimina...
Christophe; SALIN; David; RENAULT; Guy; VANNIER; Philippe; VERNON
2006-01-01
Effect of increasing ambient temperature on water loss and thermosensibility (critical thermal maximum,CTmax) was examined in last instar larvae, pupae and adults of Alphitobius diaperinus (Coleoptera: Tenebrionidae).CTmax was significantly lower in adults and pupae than in last instar larvae (last instar larvae: CTmax = 48.5 ± 0. 5℃ ,pupae: CTmax= 48.0±0.9℃ , adult: CTmax=47.8±1.1℃ ). Moreover, acclimation had no significant impact on adult CTmax. Water loss was recorded continuously between 20 and 60℃ and differed significantly among the three developmental stages. Last instar larvae and adults exhibited similar water losses with a sharp increase above a critical transition temperature (CTT), which is about 40℃. In pupae, a significantly lower rate of water loss was found, even above 40℃ . An increase of 10℃ (25 - 35℃ ) induced a 2.0 and 2.6-fold increase of the water loss in pupae and adults of A.diaperinus ( Q10 = 2.05±0.70 and 2.49±1.31, respectively) vs. 3.52±1.27 in larvae. Water loss was strongly increased over the range 35 - 45℃ in larvae and adults (Q10=6.85±1.90 and 8.51 ± 2.32). In pupae, Q10 was also increased over the range 35 - 45℃ (Q10 =3.76±1.83), but less than in larvae and adults. In A .diaperinus pupae,characterized by motionless without feeding ability, lower metabolic rate, better ability to keep the spiracles closed more often thanks to a specific structure, and the cuticular composition (surface lipids and proteins) may explain the reduced water loss [ Acta Zoologica Sinica 52 (1): 79 - 86, 2006].%本文研究了升高环境温度对小粉虫(Alphitobius diaperinus,鞘翅目拟步行虫总科)末龄幼虫、蛹以及成虫的失水和热敏性(临界热极值,Critical thermal maximum,CTmax)的影响.小粉虫成虫和蛹的CTmax值显著低于末龄幼虫(末龄幼虫:CTmax=48.5±0.5℃;蛹:CTmax=48.0±0.9℃;成虫:CTmax=47.8±1.1℃).此外,成虫的适应性对其CTmax没有显著的影响.在20至60
Tomar, Namrata; De, Rajat K
2013-01-01
Response of an immune system to a pathogen attack depends on the balance between the host immune defense and the virulence of the pathogen. Investigation of molecular interactions between the proteins of a host and a pathogen helps in identifying the pathogenic proteins. It is necessary to understand the dynamics of a normally behaved host system to evaluate the capacity of its immune system upon pathogen attack. In this study, we have compared the behavior of an unperturbed and pathogen perturbed host system. Moreover, we have developed a formalism under Flux Balance Analysis (FBA) for the optimization of conflicting objective functions. We have constructed an integrated pathway system, which includes Staphylococcal Superantigen (SAg) expression regulatory pathway and TCR signaling pathway of Homo sapiens. We have implemented the method on this pathway system and observed the behavior of host signaling molecules upon pathogen attack. The entire study has been divided into six different cases, based on the perturbed/unperturbed conditions. In other words, we have investigated unperturbed and pathogen perturbed human TCR signaling pathway, with different combinations of optimization of concentrations of regulatory and signaling molecules. One of these cases has aimed at finding out whether minimization of the toxin production in a pathogen leads to the change in the concentration levels of the proteins coded by TCR signaling pathway genes in the infected host. Based on the computed results, we have hypothesized that the balance between TCR signaling inhibitory and stimulatory molecules can keep TCR signaling system into resting/stimulating state, depending upon the perturbation. The proposed integrated host-pathogen interaction pathway model has accurately reflected the experimental evidences, which we have used for validation purpose. The significance of this kind of investigation lies in revealing the susceptible interaction points that can take back the
Kozdon, R.; Kelly, D.; Fournelle, J.; Valley, J. W.
2012-12-01
Earth surface temperatures warmed by ~5°C during an ancient (~55.5 Ma) global warming event termed the Paleocene-Eocene thermal maximum (PETM). This transient (~200 ka) "hyperthermal" climate state had profound consequences for the planet's surficial processes and biosphere, and is widely touted as being an ancient analog for climate change driven by human activities. Hallmarks of the PETM are pervasive carbonate dissolution in the ocean basins and a negative carbon isotope excursion (CIE) recorded in variety of substrates including soil and marine carbonates. Together these lines of evidence signal the rapid (≤30 ka) release of massive quantities (≥2000 Gt) of 13C-depleted carbon into the exogenic carbon cycle. Paleoenvironmental reconstructions based on pedogenic features in paleosols, clay mineralogy and sedimentology of coastal and continental deposits, and land-plant communities indicate that PETM warmth was accompanied by a major perturbation to the hydrologic cycle. Micropaleontological evidence and n-alkane hydrogen isotope records indicate that increased poleward moisture transport reduced sea-surface salinities (SSSs) in the central Arctic Ocean during the PETM. Such findings are broadly consistent with predictions of climate model simulations. Here we reassess a well-studied PETM record from the Southern Ocean (ODP Site 690) in light of new δ18O and Mg/Ca data obtained from planktic foraminiferal shells by secondary ion mass spectrometry (SIMS) and electron microprobe analysis (EMPA), respectively. The unparalleled spatial resolution of these in situ techniques permits extraction of more reliable δ18O and Mg/Ca data by targeting of minute (≤10 μm spots), biogenic domains within individual planktic foraminifera that retain the original shell chemistry (Kozdon et al. 2011, Paleocean.). In general, the stratigraphic profile and magnitude of the δ18O decrease (~2.2‰) delimiting PETM warming in our SIMS-generated record are similar to those of
Maximum likely scale estimation
Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo
2005-01-01
A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and/or ...
Maximum information photoelectron metrology
Hockett, P; Wollenhaupt, M; Baumert, T
2015-01-01
Photoelectron interferograms, manifested in photoelectron angular distributions (PADs), are a high-information, coherent observable. In order to obtain the maximum information from angle-resolved photoionization experiments it is desirable to record the full, 3D, photoelectron momentum distribution. Here we apply tomographic reconstruction techniques to obtain such 3D distributions from multiphoton ionization of potassium atoms, and fully analyse the energy and angular content of the 3D data. The PADs obtained as a function of energy indicate good agreement with previous 2D data and detailed analysis [Hockett et. al., Phys. Rev. Lett. 112, 223001 (2014)] over the main spectral features, but also indicate unexpected symmetry-breaking in certain regions of momentum space, thus revealing additional continuum interferences which cannot otherwise be observed. These observations reflect the presence of additional ionization pathways and, most generally, illustrate the power of maximum information measurements of th...
Maximum Likelihood Associative Memories
Gripon, Vincent; Rabbat, Michael
2013-01-01
Associative memories are structures that store data in such a way that it can later be retrieved given only a part of its content -- a sort-of error/erasure-resilience property. They are used in applications ranging from caches and memory management in CPUs to database engines. In this work we study associative memories built on the maximum likelihood principle. We derive minimum residual error rates when the data stored comes from a uniform binary source. Second, we determine the minimum amo...
Maximum likely scale estimation
Loog, Marco; Pedersen, Kim Steenstrup; Markussen, Bo
2005-01-01
A maximum likelihood local scale estimation principle is presented. An actual implementation of the estimation principle uses second order moments of multiple measurements at a fixed location in the image. These measurements consist of Gaussian derivatives possibly taken at several scales and....../or having different derivative orders. Although the principle is applicable to a wide variety of image models, the main focus here is on the Brownian model and its use for scale selection in natural images. Furthermore, in the examples provided, the simplifying assumption is made that the behavior...... of the measurements is completely characterized by all moments up to second order....
F. TopsÃƒÂ¸e
2001-09-01
Full Text Available Abstract: In its modern formulation, the Maximum Entropy Principle was promoted by E.T. Jaynes, starting in the mid-fifties. The principle dictates that one should look for a distribution, consistent with available information, which maximizes the entropy. However, this principle focuses only on distributions and it appears advantageous to bring information theoretical thinking more prominently into play by also focusing on the "observer" and on coding. This view was brought forward by the second named author in the late seventies and is the view we will follow-up on here. It leads to the consideration of a certain game, the Code Length Game and, via standard game theoretical thinking, to a principle of Game Theoretical Equilibrium. This principle is more basic than the Maximum Entropy Principle in the sense that the search for one type of optimal strategies in the Code Length Game translates directly into the search for distributions with maximum entropy. In the present paper we offer a self-contained and comprehensive treatment of fundamentals of both principles mentioned, based on a study of the Code Length Game. Though new concepts and results are presented, the reading should be instructional and accessible to a rather wide audience, at least if certain mathematical details are left aside at a rst reading. The most frequently studied instance of entropy maximization pertains to the Mean Energy Model which involves a moment constraint related to a given function, here taken to represent "energy". This type of application is very well known from the literature with hundreds of applications pertaining to several different elds and will also here serve as important illustration of the theory. But our approach reaches further, especially regarding the study of continuity properties of the entropy function, and this leads to new results which allow a discussion of models with so-called entropy loss. These results have tempted us to speculate over
Regularized maximum correntropy machine
Wang, Jim Jing-Yan
2015-02-12
In this paper we investigate the usage of regularized correntropy framework for learning of classifiers from noisy labels. The class label predictors learned by minimizing transitional loss functions are sensitive to the noisy and outlying labels of training samples, because the transitional loss functions are equally applied to all the samples. To solve this problem, we propose to learn the class label predictors by maximizing the correntropy between the predicted labels and the true labels of the training samples, under the regularized Maximum Correntropy Criteria (MCC) framework. Moreover, we regularize the predictor parameter to control the complexity of the predictor. The learning problem is formulated by an objective function considering the parameter regularization and MCC simultaneously. By optimizing the objective function alternately, we develop a novel predictor learning algorithm. The experiments on two challenging pattern classification tasks show that it significantly outperforms the machines with transitional loss functions.
Equalized near maximum likelihood detector
2012-01-01
This paper presents new detector that is used to mitigate intersymbol interference introduced by bandlimited channels. This detector is named equalized near maximum likelihood detector which combines nonlinear equalizer and near maximum likelihood detector. Simulation results show that the performance of equalized near maximum likelihood detector is better than the performance of nonlinear equalizer but worse than near maximum likelihood detector.
Cheeseman, Peter; Stutz, John
2005-01-01
A long standing mystery in using Maximum Entropy (MaxEnt) is how to deal with constraints whose values are uncertain. This situation arises when constraint values are estimated from data, because of finite sample sizes. One approach to this problem, advocated by E.T. Jaynes [1], is to ignore this uncertainty, and treat the empirically observed values as exact. We refer to this as the classic MaxEnt approach. Classic MaxEnt gives point probabilities (subject to the given constraints), rather than probability densities. We develop an alternative approach that assumes that the uncertain constraint values are represented by a probability density {e.g: a Gaussian), and this uncertainty yields a MaxEnt posterior probability density. That is, the classic MaxEnt point probabilities are regarded as a multidimensional function of the given constraint values, and uncertainty on these values is transmitted through the MaxEnt function to give uncertainty over the MaXEnt probabilities. We illustrate this approach by explicitly calculating the generalized MaxEnt density for a simple but common case, then show how this can be extended numerically to the general case. This paper expands the generalized MaxEnt concept introduced in a previous paper [3].
Maximum Temperature Detection System for Integrated Circuits
Frankiewicz, Maciej; Kos, Andrzej
2015-03-01
The paper describes structure and measurement results of the system detecting present maximum temperature on the surface of an integrated circuit. The system consists of the set of proportional to absolute temperature sensors, temperature processing path and a digital part designed in VHDL. Analogue parts of the circuit where designed with full-custom technique. The system is a part of temperature-controlled oscillator circuit - a power management system based on dynamic frequency scaling method. The oscillator cooperates with microprocessor dedicated for thermal experiments. The whole system is implemented in UMC CMOS 0.18 μm (1.8 V) technology.
Global change during the Paleocene-Eocene thermal maximum
Sluijs, A.
2006-01-01
Proxy data indicate that atmospheric CO2 concentrations expected for the next centuries have not been equaled since the early Paleogene, approximately 66 to 45 Million years (Ma) ago. The early Paleogene global climate appears to have been substantially warmer than that of present day, likely in re
OECD Maximum Residue Limit Calculator
With the goal of harmonizing the calculation of maximum residue limits (MRLs) across the Organisation for Economic Cooperation and Development, the OECD has developed an MRL Calculator. View the calculator.
Maximum margin Bayesian network classifiers.
Pernkopf, Franz; Wohlmayr, Michael; Tschiatschek, Sebastian
2012-03-01
We present a maximum margin parameter learning algorithm for Bayesian network classifiers using a conjugate gradient (CG) method for optimization. In contrast to previous approaches, we maintain the normalization constraints on the parameters of the Bayesian network during optimization, i.e., the probabilistic interpretation of the model is not lost. This enables us to handle missing features in discriminatively optimized Bayesian networks. In experiments, we compare the classification performance of maximum margin parameter learning to conditional likelihood and maximum likelihood learning approaches. Discriminative parameter learning significantly outperforms generative maximum likelihood estimation for naive Bayes and tree augmented naive Bayes structures on all considered data sets. Furthermore, maximizing the margin dominates the conditional likelihood approach in terms of classification performance in most cases. We provide results for a recently proposed maximum margin optimization approach based on convex relaxation. While the classification results are highly similar, our CG-based optimization is computationally up to orders of magnitude faster. Margin-optimized Bayesian network classifiers achieve classification performance comparable to support vector machines (SVMs) using fewer parameters. Moreover, we show that unanticipated missing feature values during classification can be easily processed by discriminatively optimized Bayesian network classifiers, a case where discriminative classifiers usually require mechanisms to complete unknown feature values in the data first.
Maximum Entropy in Drug Discovery
Chih-Yuan Tseng
2014-07-01
Full Text Available Drug discovery applies multidisciplinary approaches either experimentally, computationally or both ways to identify lead compounds to treat various diseases. While conventional approaches have yielded many US Food and Drug Administration (FDA-approved drugs, researchers continue investigating and designing better approaches to increase the success rate in the discovery process. In this article, we provide an overview of the current strategies and point out where and how the method of maximum entropy has been introduced in this area. The maximum entropy principle has its root in thermodynamics, yet since Jaynes’ pioneering work in the 1950s, the maximum entropy principle has not only been used as a physics law, but also as a reasoning tool that allows us to process information in hand with the least bias. Its applicability in various disciplines has been abundantly demonstrated. We give several examples of applications of maximum entropy in different stages of drug discovery. Finally, we discuss a promising new direction in drug discovery that is likely to hinge on the ways of utilizing maximum entropy.
Greenslade, Thomas B., Jr.
1985-01-01
Discusses a series of experiments performed by Thomas Hope in 1805 which show the temperature at which water has its maximum density. Early data cast into a modern form as well as guidelines and recent data collected from the author provide background for duplicating Hope's experiments in the classroom. (JN)
Abolishing the maximum tension principle
Dabrowski, Mariusz P
2015-01-01
We find the series of example theories for which the relativistic limit of maximum tension $F_{max} = c^2/4G$ represented by the entropic force can be abolished. Among them the varying constants theories, some generalized entropy models applied both for cosmological and black hole horizons as well as some generalized uncertainty principle models.
Abolishing the maximum tension principle
Mariusz P. Da̧browski
2015-09-01
Full Text Available We find the series of example theories for which the relativistic limit of maximum tension Fmax=c4/4G represented by the entropic force can be abolished. Among them the varying constants theories, some generalized entropy models applied both for cosmological and black hole horizons as well as some generalized uncertainty principle models.
Maximum Genus of Strong Embeddings
Er-ling Wei; Yan-pei Liu; Han Ren
2003-01-01
The strong embedding conjecture states that any 2-connected graph has a strong embedding on some surface. It implies the circuit double cover conjecture: Any 2-connected graph has a circuit double cover.Conversely, it is not true. But for a 3-regular graph, the two conjectures are equivalent. In this paper, a characterization of graphs having a strong embedding with exactly 3 faces, which is the strong embedding of maximum genus, is given. In addition, some graphs with the property are provided. More generally, an upper bound of the maximum genus of strong embeddings of a graph is presented too. Lastly, it is shown that the interpolation theorem is true to planar Halin graph.
Remizov, Ivan D
2009-01-01
In this note, we represent a subdifferential of a maximum functional defined on the space of all real-valued continuous functions on a given metric compact set. For a given argument, $f$ it coincides with the set of all probability measures on the set of points maximizing $f$ on the initial compact set. This complete characterization lies in the heart of several important identities in microeconomics, such as Roy's identity, Sheppard's lemma, as well as duality theory in production and linear programming.
The Testability of Maximum Magnitude
Clements, R.; Schorlemmer, D.; Gonzalez, A.; Zoeller, G.; Schneider, M.
2012-12-01
Recent disasters caused by earthquakes of unexpectedly large magnitude (such as Tohoku) illustrate the need for reliable assessments of the seismic hazard. Estimates of the maximum possible magnitude M at a given fault or in a particular zone are essential parameters in probabilistic seismic hazard assessment (PSHA), but their accuracy remains untested. In this study, we discuss the testability of long-term and short-term M estimates and the limitations that arise from testing such rare events. Of considerable importance is whether or not those limitations imply a lack of testability of a useful maximum magnitude estimate, and whether this should have any influence on current PSHA methodology. We use a simple extreme value theory approach to derive a probability distribution for the expected maximum magnitude in a future time interval, and we perform a sensitivity analysis on this distribution to determine if there is a reasonable avenue available for testing M estimates as they are commonly reported today: devoid of an appropriate probability distribution of their own and estimated only for infinite time (or relatively large untestable periods). Our results imply that any attempt at testing such estimates is futile, and that the distribution is highly sensitive to M estimates only under certain optimal conditions that are rarely observed in practice. In the future we suggest that PSHA modelers be brutally honest about the uncertainty of M estimates, or must find a way to decrease its influence on the estimated hazard.
Alternative Multiview Maximum Entropy Discrimination.
Chao, Guoqing; Sun, Shiliang
2016-07-01
Maximum entropy discrimination (MED) is a general framework for discriminative estimation based on maximum entropy and maximum margin principles, and can produce hard-margin support vector machines under some assumptions. Recently, the multiview version of MED multiview MED (MVMED) was proposed. In this paper, we try to explore a more natural MVMED framework by assuming two separate distributions p1( Θ1) over the first-view classifier parameter Θ1 and p2( Θ2) over the second-view classifier parameter Θ2 . We name the new MVMED framework as alternative MVMED (AMVMED), which enforces the posteriors of two view margins to be equal. The proposed AMVMED is more flexible than the existing MVMED, because compared with MVMED, which optimizes one relative entropy, AMVMED assigns one relative entropy term to each of the two views, thus incorporating a tradeoff between the two views. We give the detailed solving procedure, which can be divided into two steps. The first step is solving our optimization problem without considering the equal margin posteriors from two views, and then, in the second step, we consider the equal posteriors. Experimental results on multiple real-world data sets verify the effectiveness of the AMVMED, and comparisons with MVMED are also reported.
Cacti with maximum Kirchhoff index
Wang, Wen-Rui; Pan, Xiang-Feng
2015-01-01
The concept of resistance distance was first proposed by Klein and Randi\\'c. The Kirchhoff index $Kf(G)$ of a graph $G$ is the sum of resistance distance between all pairs of vertices in $G$. A connected graph $G$ is called a cactus if each block of $G$ is either an edge or a cycle. Let $Cat(n;t)$ be the set of connected cacti possessing $n$ vertices and $t$ cycles, where $0\\leq t \\leq \\lfloor\\frac{n-1}{2}\\rfloor$. In this paper, the maximum kirchhoff index of cacti are characterized, as well...
Generic maximum likely scale selection
Pedersen, Kim Steenstrup; Loog, Marco; Markussen, Bo
2007-01-01
The fundamental problem of local scale selection is addressed by means of a novel principle, which is based on maximum likelihood estimation. The principle is generally applicable to a broad variety of image models and descriptors, and provides a generic scale estimation methodology. The focus...... on second order moments of multiple measurements outputs at a fixed location. These measurements, which reflect local image structure, consist in the cases considered here of Gaussian derivatives taken at several scales and/or having different derivative orders....
Danilo F. Pereira
2005-08-01
Full Text Available Considerando o comportamento social, é sugestivo que a freqüência e a intensidade de interações agressivas, o total de coesão social e compreensão da extensão de vícios sociais possam ser utilizados para avaliação de bem-estar. Este trabalho propõe que a freqüência de utilização de determinados locais dentro do galpão possa ser usada como variável para monitorar estados de bem-estar térmico e/ou estresse das aves alojadas. A partir de dados registrados no verão de 2000-2001, esta pesquisa identificou as temperaturas críticas máximas (tc máx de matrizes pesadas, individualmente, por meio de análise estatística da freqüência de uso de locais previamente estabelecidos, utilizando a tecnologia de identificação eletrônica. Os valores das tc máx individuais variaram de 30 °C ± 0,2 ºC a 32,3 ºC ± 0,2 ºC e a temperatura crítica máxima média para o grupo foi 30,9 ºC ± 0,8 ºC.Considering the social behavior, it is suggested that the frequency and the intensity of aggressive interactions, as the well as the total social cohesion, and the understanding of social behavior can be used for welfare evaluation. This research proposes that the frequency of use of specific places inside the bird's housing can be used as variable to monitor thermal welfare status and/or the stress level of the lodged birds. From data registered in the summer of 2000/2001, this study identified the maximum critical temperatures (ct max of the female broiler breeders individually, using statistical analysis of the use of previously determined places, applying the technology of electronic identification. The ct max values varied from 30 °C ± 0,2 ºC to 32,3 ºC ± 0,2 ºC and the critical temperature maximum average for the group was 30,9 ºC ± 0,8 ºC.
Economics and Maximum Entropy Production
Lorenz, R. D.
2003-04-01
Price differentials, sales volume and profit can be seen as analogues of temperature difference, heat flow and work or entropy production in the climate system. One aspect in which economic systems exhibit more clarity than the climate is that the empirical and/or statistical mechanical tendency for systems to seek a maximum in production is very evident in economics, in that the profit motive is very clear. Noting the common link between 1/f noise, power laws and Self-Organized Criticality with Maximum Entropy Production, the power law fluctuations in security and commodity prices is not inconsistent with the analogy. There is an additional thermodynamic analogy, in that scarcity is valued. A commodity concentrated among a few traders is valued highly by the many who do not have it. The market therefore encourages via prices the spreading of those goods among a wider group, just as heat tends to diffuse, increasing entropy. I explore some empirical price-volume relationships of metals and meteorites in this context.
Objects of maximum electromagnetic chirality
Fernandez-Corbaton, Ivan
2015-01-01
We introduce a definition of the electromagnetic chirality of an object and show that it has an upper bound. The upper bound is attained if and only if the object is transparent for fields of one handedness (helicity). Additionally, electromagnetic duality symmetry, i.e. helicity preservation upon scattering, turns out to be a necessary condition for reciprocal scatterers to attain the upper bound. We use these results to provide requirements for the design of such extremal scatterers. The requirements can be formulated as constraints on the polarizability tensors for dipolar scatterers or as material constitutive relations. We also outline two applications for objects of maximum electromagnetic chirality: A twofold resonantly enhanced and background free circular dichroism measurement setup, and angle independent helicity filtering glasses.
Maximum mutual information regularized classification
Wang, Jim Jing-Yan
2014-09-07
In this paper, a novel pattern classification approach is proposed by regularizing the classifier learning to maximize mutual information between the classification response and the true class label. We argue that, with the learned classifier, the uncertainty of the true class label of a data sample should be reduced by knowing its classification response as much as possible. The reduced uncertainty is measured by the mutual information between the classification response and the true class label. To this end, when learning a linear classifier, we propose to maximize the mutual information between classification responses and true class labels of training samples, besides minimizing the classification error and reducing the classifier complexity. An objective function is constructed by modeling mutual information with entropy estimation, and it is optimized by a gradient descend method in an iterative algorithm. Experiments on two real world pattern classification problems show the significant improvements achieved by maximum mutual information regularization.
The strong maximum principle revisited
Pucci, Patrizia; Serrin, James
In this paper we first present the classical maximum principle due to E. Hopf, together with an extended commentary and discussion of Hopf's paper. We emphasize the comparison technique invented by Hopf to prove this principle, which has since become a main mathematical tool for the study of second order elliptic partial differential equations and has generated an enormous number of important applications. While Hopf's principle is generally understood to apply to linear equations, it is in fact also crucial in nonlinear theories, such as those under consideration here. In particular, we shall treat and discuss recent generalizations of the strong maximum principle, and also the compact support principle, for the case of singular quasilinear elliptic differential inequalities, under generally weak assumptions on the quasilinear operators and the nonlinearities involved. Our principal interest is in necessary and sufficient conditions for the validity of both principles; in exposing and simplifying earlier proofs of corresponding results; and in extending the conclusions to wider classes of singular operators than previously considered. The results have unexpected ramifications for other problems, as will develop from the exposition, e.g. two point boundary value problems for singular quasilinear ordinary differential equations (Sections 3 and 4); the exterior Dirichlet boundary value problem (Section 5); the existence of dead cores and compact support solutions, i.e. dead cores at infinity (Section 7); Euler-Lagrange inequalities on a Riemannian manifold (Section 9); comparison and uniqueness theorems for solutions of singular quasilinear differential inequalities (Section 10). The case of p-regular elliptic inequalities is briefly considered in Section 11.
Maximum entropy production in daisyworld
Maunu, Haley A.; Knuth, Kevin H.
2012-05-01
Daisyworld was first introduced in 1983 by Watson and Lovelock as a model that illustrates how life can influence a planet's climate. These models typically involve modeling a planetary surface on which black and white daisies can grow thus influencing the local surface albedo and therefore also the temperature distribution. Since then, variations of daisyworld have been applied to study problems ranging from ecological systems to global climate. Much of the interest in daisyworld models is due to the fact that they enable one to study self-regulating systems. These models are nonlinear, and as such they exhibit sensitive dependence on initial conditions, and depending on the specifics of the model they can also exhibit feedback loops, oscillations, and chaotic behavior. Many daisyworld models are thermodynamic in nature in that they rely on heat flux and temperature gradients. However, what is not well-known is whether, or even why, a daisyworld model might settle into a maximum entropy production (MEP) state. With the aim to better understand these systems, this paper will discuss what is known about the role of MEP in daisyworld models.
Maximum stellar iron core mass
F W Giacobbe
2003-03-01
An analytical method of estimating the mass of a stellar iron core, just prior to core collapse, is described in this paper. The method employed depends, in part, upon an estimate of the true relativistic mass increase experienced by electrons within a highly compressed iron core, just prior to core collapse, and is signiﬁcantly different from a more typical Chandrasekhar mass limit approach. This technique produced a maximum stellar iron core mass value of 2.69 × 1030 kg (1.35 solar masses). This mass value is very near to the typical mass values found for neutron stars in a recent survey of actual neutron star masses. Although slightly lower and higher neutron star masses may also be found, lower mass neutron stars are believed to be formed as a result of enhanced iron core compression due to the weight of non-ferrous matter overlying the iron cores within large stars. And, higher mass neutron stars are likely to be formed as a result of fallback or accretion of additional matter after an initial collapse event involving an iron core having a mass no greater than 2.69 × 1030 kg.
Maximum Matchings via Glauber Dynamics
Jindal, Anant; Pal, Manjish
2011-01-01
In this paper we study the classic problem of computing a maximum cardinality matching in general graphs $G = (V, E)$. The best known algorithm for this problem till date runs in $O(m \\sqrt{n})$ time due to Micali and Vazirani \\cite{MV80}. Even for general bipartite graphs this is the best known running time (the algorithm of Karp and Hopcroft \\cite{HK73} also achieves this bound). For regular bipartite graphs one can achieve an $O(m)$ time algorithm which, following a series of papers, has been recently improved to $O(n \\log n)$ by Goel, Kapralov and Khanna (STOC 2010) \\cite{GKK10}. In this paper we present a randomized algorithm based on the Markov Chain Monte Carlo paradigm which runs in $O(m \\log^2 n)$ time, thereby obtaining a significant improvement over \\cite{MV80}. We use a Markov chain similar to the \\emph{hard-core model} for Glauber Dynamics with \\emph{fugacity} parameter $\\lambda$, which is used to sample independent sets in a graph from the Gibbs Distribution \\cite{V99}, to design a faster algori...
2011-01-10
...: Establishing Maximum Allowable Operating Pressure or Maximum Operating Pressure Using Record Evidence, and... facilities of their responsibilities, under Federal integrity management (IM) regulations, to perform... system, especially when calculating Maximum Allowable Operating Pressure (MAOP) or Maximum Operating...
The Sherpa Maximum Likelihood Estimator
Nguyen, D.; Doe, S.; Evans, I.; Hain, R.; Primini, F.
2011-07-01
A primary goal for the second release of the Chandra Source Catalog (CSC) is to include X-ray sources with as few as 5 photon counts detected in stacked observations of the same field, while maintaining acceptable detection efficiency and false source rates. Aggressive source detection methods will result in detection of many false positive source candidates. Candidate detections will then be sent to a new tool, the Maximum Likelihood Estimator (MLE), to evaluate the likelihood that a detection is a real source. MLE uses the Sherpa modeling and fitting engine to fit a model of a background and source to multiple overlapping candidate source regions. A background model is calculated by simultaneously fitting the observed photon flux in multiple background regions. This model is used to determine the quality of the fit statistic for a background-only hypothesis in the potential source region. The statistic for a background-plus-source hypothesis is calculated by adding a Gaussian source model convolved with the appropriate Chandra point spread function (PSF) and simultaneously fitting the observed photon flux in each observation in the stack. Since a candidate source may be located anywhere in the field of view of each stacked observation, a different PSF must be used for each observation because of the strong spatial dependence of the Chandra PSF. The likelihood of a valid source being detected is a function of the two statistics (for background alone, and for background-plus-source). The MLE tool is an extensible Python module with potential for use by the general Chandra user.
Vestige: Maximum likelihood phylogenetic footprinting
Maxwell Peter
2005-05-01
Full Text Available Abstract Background Phylogenetic footprinting is the identification of functional regions of DNA by their evolutionary conservation. This is achieved by comparing orthologous regions from multiple species and identifying the DNA regions that have diverged less than neutral DNA. Vestige is a phylogenetic footprinting package built on the PyEvolve toolkit that uses probabilistic molecular evolutionary modelling to represent aspects of sequence evolution, including the conventional divergence measure employed by other footprinting approaches. In addition to measuring the divergence, Vestige allows the expansion of the definition of a phylogenetic footprint to include variation in the distribution of any molecular evolutionary processes. This is achieved by displaying the distribution of model parameters that represent partitions of molecular evolutionary substitutions. Examination of the spatial incidence of these effects across regions of the genome can identify DNA segments that differ in the nature of the evolutionary process. Results Vestige was applied to a reference dataset of the SCL locus from four species and provided clear identification of the known conserved regions in this dataset. To demonstrate the flexibility to use diverse models of molecular evolution and dissect the nature of the evolutionary process Vestige was used to footprint the Ka/Ks ratio in primate BRCA1 with a codon model of evolution. Two regions of putative adaptive evolution were identified illustrating the ability of Vestige to represent the spatial distribution of distinct molecular evolutionary processes. Conclusion Vestige provides a flexible, open platform for phylogenetic footprinting. Underpinned by the PyEvolve toolkit, Vestige provides a framework for visualising the signatures of evolutionary processes across the genome of numerous organisms simultaneously. By exploiting the maximum-likelihood statistical framework, the complex interplay between mutational
Faucheux, L. P.; Bourdieu, L. S.; Kaplan, P. D.; Libchaber, A. J.
1995-02-01
We present an optical realization of a thermal ratchet. Directed motion of Brownian particles in water is induced by modulating in time a spatially periodic but asymmetric optical potential. The net drift shows a maximum as a function of the modulation period. The experimental results agree with a simple theoretical model based on diffusion.
Effect of enhanced thermal dissipation on the Rayleigh-Taylor instability in emulsion-like media
Toor, A.; Ryutov, D.
1997-07-01
Rayleigh-Taylor instability in a finely structured emulsion-like medium consisting of the two components of different compressibility is considered. Although the term ``emulsion`` is used to describe the structure of the medium, under typical fast Z-pinch conditions both components behave as gases. The two components are chosen in such a way that their densities in the unperturbed state are approximately equal. Specific emphasis has been made on the analysis of perturbations with the scale {lambda} considerably exceeding the size of the grains a. Averaged equations describing such perturbations am derived. The difference in compressibility of the two components leads to the formation of temperature variations at the scale a, and increases the rate of the thermal dissipation by a factor ({lambda}/a){sup 2}. The strongest stabilizing effect of the thermal dissipation takes place when the thermal relaxation time is comparable with the instability growth rate.
Beausoleil, R G; Kells, W; Camp, J; Gustafson, E K; Fejer, M M
2002-01-01
We develop a steady-state analytical and numerical model of the optical response of power-recycled Fabry-Perot Michelson laser gravitational-wave detectors to thermal focusing in optical substrates. We assume that the thermal distortions are small enough that we can represent the unperturbed intracavity field anywhere in the detector as a linear combination of basis functions related to the eigenmodes of one of the Fabry-Perot arm cavities, and we take great care to preserve numerically the nearly ideal longitudinal phase resonance conditions that would otherwise be provided by an external servo-locking control system. We have included the effects of nonlinear thermal focusing due to power absorption in both the substrates and coatings of the mirrors and beamsplitter, the effects of a finite mismatch between the curvatures of the laser wavefront and the mirror surface, and the diffraction by the mirror aperture at each instance of reflection and transmission. We demonstrate a detailed numerical example of thi...
Receiver function estimated by maximum entropy deconvolution
吴庆举; 田小波; 张乃铃; 李卫平; 曾融生
2003-01-01
Maximum entropy deconvolution is presented to estimate receiver function, with the maximum entropy as the rule to determine auto-correlation and cross-correlation functions. The Toeplitz equation and Levinson algorithm are used to calculate the iterative formula of error-predicting filter, and receiver function is then estimated. During extrapolation, reflective coefficient is always less than 1, which keeps maximum entropy deconvolution stable. The maximum entropy of the data outside window increases the resolution of receiver function. Both synthetic and real seismograms show that maximum entropy deconvolution is an effective method to measure receiver function in time-domain.
Philip D.GINGERICH
2010-01-01
The late Professor Minchen Chow started his career in vertebrate paleontology with a team of scholars working to clarify the biostratigraphy and paleogeography of Paleocene-Eocene change in man-malian faunas.The Paleocene-Eocene transition is the time of first appearance of artiodactyls.perisso-dactyls.and primates (APP taxa)in the fossil record.Recognition of the Paleocene as an epoch sepa-rate from the Eocene started to be accepted in 1911 following discovery of a new Clarkforkian latest-Pa-leocene mammalian fauna at Polecat Bench in western North America.Later the Paleocene-Eoceneboundary was shown to include an interval with dwarfed mammalian lineages.A Paleocene-Eocene car-bon isotope excursion (CIE) was discovered coincident with both mammalian dwarfing and the first ap-pearance of APP taxa.This enabled global generalization of the CIE,which was linked in turn to the Paleocene-Eocene thermal maximum(PETM).The PETM is a global greenhouse warming event that had transient effects on the earth's climate and biota,but also profound lasting effects on the biota.Much of what we know about mammals in relation to the CIE and PETM we have learned through high-resolution study of the exceptional stratigraphic record flanking Polecat Bench,where Professor Chow worked early in his career and where his ashes now lie.%跟随一队研究哺乳动物群在古新世-始新世变化的生物地层学和古地理学的学者,已故周明镇教授开始了他的古脊椎动物学事业.这是化石记录中偶蹄类、奇蹄类和灵长类(APP类群)首次出现的时期.随着北美西部Polecat Bench新的最晚古新世Clarkforkian哺乳动物群的发现,古新世作为一个独立于始新世的分期从1911年开始被接受.后来,研究证明古新世-始新世界线包括了一段时间,这期间发育了矮小型哺乳动物支系.古新世-始新世碳同位素漂移(CIE)与哺乳动物矮小化以及APP类群的首次出现是同时的.据此可以对CIE进行全球
Maximum Work of Free-Piston Stirling Engine Generators
Kojima, Shinji
2017-04-01
Using the method of adjoint equations described in Ref. [1], we have calculated the maximum thermal efficiencies that are theoretically attainable by free-piston Stirling and Carnot engine generators by considering the work loss due to friction and Joule heat. The net work done by the Carnot cycle is negative even when the duration of heat addition is optimized to give the maximum amount of heat addition, which is the same situation for the Brayton cycle described in our previous paper. For the Stirling cycle, the net work done is positive, and the thermal efficiency is greater than that of the Otto cycle described in our previous paper by a factor of about 2.7-1.4 for compression ratios of 5-30. The Stirling cycle is much better than the Otto, Brayton, and Carnot cycles. We have found that the optimized piston trajectories of the isothermal, isobaric, and adiabatic processes are the same when the compression ratio and the maximum volume of the same working fluid of the three processes are the same, which has facilitated the present analysis because the optimized piston trajectories of the Carnot and Stirling cycles are the same as those of the Brayton and Otto cycles, respectively.
Maximum Power from a Solar Panel
Michael Miller
2010-01-01
Full Text Available Solar energy has become a promising alternative to conventional fossil fuel sources. Solar panels are used to collect solar radiation and convert it into electricity. One of the techniques used to maximize the effectiveness of this energy alternative is to maximize the power output of the solar collector. In this project the maximum power is calculated by determining the voltage and the current of maximum power. These quantities are determined by finding the maximum value for the equation for power using differentiation. After the maximum values are found for each time of day, each individual quantity, voltage of maximum power, current of maximum power, and maximum power is plotted as a function of the time of day.
Maximum work extraction and implementation costs for nonequilibrium Maxwell's demons
Sandberg, Henrik; Delvenne, Jean-Charles; Newton, Nigel J.; Mitter, Sanjoy K.
2014-10-01
We determine the maximum amount of work extractable in finite time by a demon performing continuous measurements on a quadratic Hamiltonian system subjected to thermal fluctuations, in terms of the information extracted from the system. The maximum work demon is found to apply a high-gain continuous feedback involving a Kalman-Bucy estimate of the system state and operates in nonequilibrium. A simple and concrete electrical implementation of the feedback protocol is proposed, which allows for analytic expressions of the flows of energy, entropy, and information inside the demon. This let us show that any implementation of the demon must necessarily include an external power source, which we prove both from classical thermodynamics arguments and from a version of Landauer's memory erasure argument extended to nonequilibrium linear systems.
The inverse maximum dynamic flow problem
BAGHERIAN; Mehri
2010-01-01
We consider the inverse maximum dynamic flow (IMDF) problem.IMDF problem can be described as: how to change the capacity vector of a dynamic network as little as possible so that a given feasible dynamic flow becomes a maximum dynamic flow.After discussing some characteristics of this problem,it is converted to a constrained minimum dynamic cut problem.Then an efficient algorithm which uses two maximum dynamic flow algorithms is proposed to solve the problem.
Maximum permissible voltage of YBCO coated conductors
Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z. [Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China); Hong, Z., E-mail: zhiyong.hong@sjtu.edu.cn [Department of Electrical Engineering, Shanghai Jiao Tong University, Shanghai (China); Wang, D.; Zhou, H.; Shen, X.; Shen, C. [Qingpu Power Supply Company, State Grid Shanghai Municipal Electric Power Company, Shanghai (China)
2014-06-15
Highlights: • We examine three kinds of tapes’ maximum permissible voltage. • We examine the relationship between quenching duration and maximum permissible voltage. • Continuous I{sub c} degradations under repetitive quenching where tapes reaching maximum permissible voltage. • The relationship between maximum permissible voltage and resistance, temperature. - Abstract: Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (I{sub c}) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the I{sub c} degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.
Generalised maximum entropy and heterogeneous technologies
Oude Lansink, A.G.J.M.
1999-01-01
Generalised maximum entropy methods are used to estimate a dual model of production on panel data of Dutch cash crop farms over the period 1970-1992. The generalised maximum entropy approach allows a coherent system of input demand and output supply equations to be estimated for each farm in the sam
20 CFR 229.48 - Family maximum.
2010-04-01
... month on one person's earnings record is limited. This limited amount is called the family maximum. The family maximum used to adjust the social security overall minimum rate is based on the employee's Overall..., when any of the persons entitled to benefits on the insured individual's compensation would, except...
The maximum rotation of a galactic disc
Bottema, R
1997-01-01
The observed stellar velocity dispersions of galactic discs show that the maximum rotation of a disc is on average 63% of the observed maximum rotation. This criterion can, however, not be applied to small or low surface brightness (LSB) galaxies because such systems show, in general, a continuously
Duality of Maximum Entropy and Minimum Divergence
Shinto Eguchi
2014-06-01
Full Text Available We discuss a special class of generalized divergence measures by the use of generator functions. Any divergence measure in the class is separated into the difference between cross and diagonal entropy. The diagonal entropy measure in the class associates with a model of maximum entropy distributions; the divergence measure leads to statistical estimation via minimization, for arbitrarily giving a statistical model. The dualistic relationship between the maximum entropy model and the minimum divergence estimation is explored in the framework of information geometry. The model of maximum entropy distributions is characterized to be totally geodesic with respect to the linear connection associated with the divergence. A natural extension for the classical theory for the maximum likelihood method under the maximum entropy model in terms of the Boltzmann-Gibbs-Shannon entropy is given. We discuss the duality in detail for Tsallis entropy as a typical example.
Estimation of Maximum Allowable PV Connection to LV Residential Power Networks
Demirok, Erhan; Sera, Dezso; Teodorescu, Remus
2011-01-01
transformer or using solar inverters with new grid support features. This study presents a methodology for the estimation of maximum PV hosting capacity including IEC 60076-7 based thermal model of distribution transformer. Certain part of a real distribution network of Braedstrup suburban area in Denmark...... is used in simulation as a case study model. Furthermore, varying solutions (utilizing thermally upgraded insulation paper in transformers, reactive power services from solar inverters, etc.) are implemented on the network under investigation to examine PV penetration level and finally key results learnt......Maximum photovoltaic (PV) hosting capacity of low voltage (LV) power networks is mainly restricted by either thermal limits of network components or grid voltage quality resulted from high penetration of distributed PV systems. This maximum hosting capacity may be lower than the available solar...
Osburn, L
2010-01-01
Full Text Available Thermal comfort is influenced by environmental parameters as well as other influences including asymmetric heating and cooling conditions. Additionally, some aspects of thermal comfort may be exploited so as to enable a building to operate within a...
Thermal Properties of oil sand
LEE, Y.; Lee, H.; Kwon, Y.; Kim, J.
2013-12-01
Thermal recovery methods such as Cyclic Steam Injection or Steam Assisted Gravity Drainage (SAGD) are the effective methods for producing heavy oil or bitumen. In any thermal recovery methods, thermal properties (e.g., thermal conductivity, thermal diffusivity, and volumetric heat capacity) are closely related to the formation and expansion of steam chamber within a reservoir, which is key factors to control efficiency of thermal recovery. However, thermal properties of heavy oil or bitumen have not been well-studied despite their importance in thermal recovery methods. We measured thermal conductivity, thermal diffusivity, and volumetric heat capacity of 43 oil sand samples from Athabasca, Canada, using a transient thermal property measurement instrument. Thermal conductivity of 43 oil sand samples varies from 0.74 W/mK to 1.57 W/mK with the mean thermal conductivity of 1.09 W/mK. The mean thermal diffusivity is 5.7×10-7 m2/s with the minimum value of 4.2×10-7 m2/s and the maximum value of 8.0×10-7 m2/s. Volumetric heat capacity varies from 1.5×106 J/m3K to 2.11×106 J/m3K with the mean volumetric heat capacity of 1.91×106 J/m3K. In addition, physical and chemical properties (e.g., bitumen content, electric resistivity, porosity, gamma ray and so on) of oil sand samples have been measured by geophysical logging and in the laboratory. We are now proceeding to investigate the relationship between thermal properties and physical/chemical properties of oil sand.
A dual method for maximum entropy restoration
Smith, C. B.
1979-01-01
A simple iterative dual algorithm for maximum entropy image restoration is presented. The dual algorithm involves fewer parameters than conventional minimization in the image space. Minicomputer test results for Fourier synthesis with inadequate phantom data are given.
Maximum Throughput in Multiple-Antenna Systems
Zamani, Mahdi
2012-01-01
The point-to-point multiple-antenna channel is investigated in uncorrelated block fading environment with Rayleigh distribution. The maximum throughput and maximum expected-rate of this channel are derived under the assumption that the transmitter is oblivious to the channel state information (CSI), however, the receiver has perfect CSI. First, we prove that in multiple-input single-output (MISO) channels, the optimum transmission strategy maximizing the throughput is to use all available antennas and perform equal power allocation with uncorrelated signals. Furthermore, to increase the expected-rate, multi-layer coding is applied. Analogously, we establish that sending uncorrelated signals and performing equal power allocation across all available antennas at each layer is optimum. A closed form expression for the maximum continuous-layer expected-rate of MISO channels is also obtained. Moreover, we investigate multiple-input multiple-output (MIMO) channels, and formulate the maximum throughput in the asympt...
Photoemission spectromicroscopy with MAXIMUM at Wisconsin
Ng, W.; Ray-Chaudhuri, A.K.; Cole, R.K.; Wallace, J.; Crossley, S.; Crossley, D.; Chen, G.; Green, M.; Guo, J.; Hansen, R.W.C.; Cerrina, F.; Margaritondo, G. (Dept. of Electrical Engineering, Dept. of Physics and Synchrotron Radiation Center, Univ. of Wisconsin, Madison (USA)); Underwood, J.H.; Korthright, J.; Perera, R.C.C. (Center for X-ray Optics, Accelerator and Fusion Research Div., Lawrence Berkeley Lab., CA (USA))
1990-06-01
We describe the development of the scanning photoemission spectromicroscope MAXIMUM at the Wisoncsin Synchrotron Radiation Center, which uses radiation from a 30-period undulator. The article includes a discussion of the first tests after the initial commissioning. (orig.).
Maximum-likelihood method in quantum estimation
Paris, M G A; Sacchi, M F
2001-01-01
The maximum-likelihood method for quantum estimation is reviewed and applied to the reconstruction of density matrix of spin and radiation as well as to the determination of several parameters of interest in quantum optics.
The maximum entropy technique. System's statistical description
Belashev, B Z
2002-01-01
The maximum entropy technique (MENT) is applied for searching the distribution functions of physical values. MENT takes into consideration the demand of maximum entropy, the characteristics of the system and the connection conditions, naturally. It is allowed to apply MENT for statistical description of closed and open systems. The examples in which MENT had been used for the description of the equilibrium and nonequilibrium states and the states far from the thermodynamical equilibrium are considered
19 CFR 114.23 - Maximum period.
2010-04-01
... 19 Customs Duties 1 2010-04-01 2010-04-01 false Maximum period. 114.23 Section 114.23 Customs... CARNETS Processing of Carnets § 114.23 Maximum period. (a) A.T.A. carnet. No A.T.A. carnet with a period of validity exceeding 1 year from date of issue shall be accepted. This period of validity cannot be...
Maximum-Likelihood Detection Of Noncoherent CPM
Divsalar, Dariush; Simon, Marvin K.
1993-01-01
Simplified detectors proposed for use in maximum-likelihood-sequence detection of symbols in alphabet of size M transmitted by uncoded, full-response continuous phase modulation over radio channel with additive white Gaussian noise. Structures of receivers derived from particular interpretation of maximum-likelihood metrics. Receivers include front ends, structures of which depends only on M, analogous to those in receivers of coherent CPM. Parts of receivers following front ends have structures, complexity of which would depend on N.
SEXUAL DIMORPHISM OF MAXIMUM FEMORAL LENGTH
Pandya A M
2011-04-01
Full Text Available Sexual identification from the skeletal parts has medico legal and anthropological importance. Present study aims to obtain values of maximum femoral length and to evaluate its possible usefulness in determining correct sexual identification. Study sample consisted of 184 dry, normal, adult, human femora (136 male & 48 female from skeletal collections of Anatomy department, M. P. Shah Medical College, Jamnagar, Gujarat. Maximum length of femur was considered as maximum vertical distance between upper end of head of femur and the lowest point on femoral condyle, measured with the osteometric board. Mean Values obtained were, 451.81 and 417.48 for right male and female, and 453.35 and 420.44 for left male and female respectively. Higher value in male was statistically highly significant (P< 0.001 on both sides. Demarking point (D.P. analysis of the data showed that right femora with maximum length more than 476.70 were definitely male and less than 379.99 were definitely female; while for left bones, femora with maximum length more than 484.49 were definitely male and less than 385.73 were definitely female. Maximum length identified 13.43% of right male femora, 4.35% of right female femora, 7.25% of left male femora and 8% of left female femora. [National J of Med Res 2011; 1(2.000: 67-70
The maximum rotation of a galactic disc
Bottema, R
1997-01-01
The observed stellar velocity dispersions of galactic discs show that the maximum rotation of a disc is on average 63% of the observed maximum rotation. This criterion can, however, not be applied to small or low surface brightness (LSB) galaxies because such systems show, in general, a continuously rising rotation curve until the outermost measured radial position. That is why a general relation has been derived, giving the maximum rotation for a disc depending on the luminosity, surface brightness, and colour of the disc. As a physical basis of this relation serves an adopted fixed mass-to-light ratio as a function of colour. That functionality is consistent with results from population synthesis models and its absolute value is determined from the observed stellar velocity dispersions. The derived maximum disc rotation is compared with a number of observed maximum rotations, clearly demonstrating the need for appreciable amounts of dark matter in the disc region and even more so for LSB galaxies. Matters h...
Maximum permissible voltage of YBCO coated conductors
Wen, J.; Lin, B.; Sheng, J.; Xu, J.; Jin, Z.; Hong, Z.; Wang, D.; Zhou, H.; Shen, X.; Shen, C.
2014-06-01
Superconducting fault current limiter (SFCL) could reduce short circuit currents in electrical power system. One of the most important thing in developing SFCL is to find out the maximum permissible voltage of each limiting element. The maximum permissible voltage is defined as the maximum voltage per unit length at which the YBCO coated conductors (CC) do not suffer from critical current (Ic) degradation or burnout. In this research, the time of quenching process is changed and voltage is raised until the Ic degradation or burnout happens. YBCO coated conductors test in the experiment are from American superconductor (AMSC) and Shanghai Jiao Tong University (SJTU). Along with the quenching duration increasing, the maximum permissible voltage of CC decreases. When quenching duration is 100 ms, the maximum permissible of SJTU CC, 12 mm AMSC CC and 4 mm AMSC CC are 0.72 V/cm, 0.52 V/cm and 1.2 V/cm respectively. Based on the results of samples, the whole length of CCs used in the design of a SFCL can be determined.
Computing Rooted and Unrooted Maximum Consistent Supertrees
van Iersel, Leo
2009-01-01
A chief problem in phylogenetics and database theory is the computation of a maximum consistent tree from a set of rooted or unrooted trees. A standard input are triplets, rooted binary trees on three leaves, or quartets, unrooted binary trees on four leaves. We give exact algorithms constructing rooted and unrooted maximum consistent supertrees in time O(2^n n^5 m^2 log(m)) for a set of m triplets (quartets), each one distinctly leaf-labeled by some subset of n labels. The algorithms extend to weighted triplets (quartets). We further present fast exact algorithms for constructing rooted and unrooted maximum consistent trees in polynomial space. Finally, for a set T of m rooted or unrooted trees with maximum degree D and distinctly leaf-labeled by some subset of a set L of n labels, we compute, in O(2^{mD} n^m m^5 n^6 log(m)) time, a tree distinctly leaf-labeled by a maximum-size subset X of L that all trees in T, when restricted to X, are consistent with.
Maximum magnitude earthquakes induced by fluid injection
McGarr, Arthur F.
2014-01-01
Analysis of numerous case histories of earthquake sequences induced by fluid injection at depth reveals that the maximum magnitude appears to be limited according to the total volume of fluid injected. Similarly, the maximum seismic moment seems to have an upper bound proportional to the total volume of injected fluid. Activities involving fluid injection include (1) hydraulic fracturing of shale formations or coal seams to extract gas and oil, (2) disposal of wastewater from these gas and oil activities by injection into deep aquifers, and (3) the development of enhanced geothermal systems by injecting water into hot, low-permeability rock. Of these three operations, wastewater disposal is observed to be associated with the largest earthquakes, with maximum magnitudes sometimes exceeding 5. To estimate the maximum earthquake that could be induced by a given fluid injection project, the rock mass is assumed to be fully saturated, brittle, to respond to injection with a sequence of earthquakes localized to the region weakened by the pore pressure increase of the injection operation and to have a Gutenberg-Richter magnitude distribution with a b value of 1. If these assumptions correctly describe the circumstances of the largest earthquake, then the maximum seismic moment is limited to the volume of injected liquid times the modulus of rigidity. Observations from the available case histories of earthquakes induced by fluid injection are consistent with this bound on seismic moment. In view of the uncertainties in this analysis, however, this should not be regarded as an absolute physical limit.
Maximum magnitude earthquakes induced by fluid injection
McGarr, A.
2014-02-01
Analysis of numerous case histories of earthquake sequences induced by fluid injection at depth reveals that the maximum magnitude appears to be limited according to the total volume of fluid injected. Similarly, the maximum seismic moment seems to have an upper bound proportional to the total volume of injected fluid. Activities involving fluid injection include (1) hydraulic fracturing of shale formations or coal seams to extract gas and oil, (2) disposal of wastewater from these gas and oil activities by injection into deep aquifers, and (3) the development of enhanced geothermal systems by injecting water into hot, low-permeability rock. Of these three operations, wastewater disposal is observed to be associated with the largest earthquakes, with maximum magnitudes sometimes exceeding 5. To estimate the maximum earthquake that could be induced by a given fluid injection project, the rock mass is assumed to be fully saturated, brittle, to respond to injection with a sequence of earthquakes localized to the region weakened by the pore pressure increase of the injection operation and to have a Gutenberg-Richter magnitude distribution with a b value of 1. If these assumptions correctly describe the circumstances of the largest earthquake, then the maximum seismic moment is limited to the volume of injected liquid times the modulus of rigidity. Observations from the available case histories of earthquakes induced by fluid injection are consistent with this bound on seismic moment. In view of the uncertainties in this analysis, however, this should not be regarded as an absolute physical limit.
Ocean Thermal Extractable Energy Visualization
Ascari, Matthew [Lockheed Martin Corporation, Bethesda, MD (United States)
2012-10-28
The Ocean Thermal Extractable Energy Visualization (OTEEV) project focuses on assessing the Maximum Practicably Extractable Energy (MPEE) from the world’s ocean thermal resources. MPEE is defined as being sustainable and technically feasible, given today’s state-of-the-art ocean energy technology. Under this project the OTEEV team developed a comprehensive Geospatial Information System (GIS) dataset and software tool, and used the tool to provide a meaningful assessment of MPEE from the global and domestic U.S. ocean thermal resources.
Maximum Multiflow in Wireless Network Coding
Zhou, Jin-Yi; Jiang, Yong; Zheng, Hai-Tao
2012-01-01
In a multihop wireless network, wireless interference is crucial to the maximum multiflow (MMF) problem, which studies the maximum throughput between multiple pairs of sources and sinks. In this paper, we observe that network coding could help to decrease the impacts of wireless interference, and propose a framework to study the MMF problem for multihop wireless networks with network coding. Firstly, a network model is set up to describe the new conflict relations modified by network coding. Then, we formulate a linear programming problem to compute the maximum throughput and show its superiority over one in networks without coding. Finally, the MMF problem in wireless network coding is shown to be NP-hard and a polynomial approximation algorithm is proposed.
The Wiener maximum quadratic assignment problem
Cela, Eranda; Woeginger, Gerhard J
2011-01-01
We investigate a special case of the maximum quadratic assignment problem where one matrix is a product matrix and the other matrix is the distance matrix of a one-dimensional point set. We show that this special case, which we call the Wiener maximum quadratic assignment problem, is NP-hard in the ordinary sense and solvable in pseudo-polynomial time. Our approach also yields a polynomial time solution for the following problem from chemical graph theory: Find a tree that maximizes the Wiener index among all trees with a prescribed degree sequence. This settles an open problem from the literature.
Maximum confidence measurements via probabilistic quantum cloning
Zhang Wen-Hai; Yu Long-Bao; Cao Zhuo-Liang; Ye Liu
2013-01-01
Probabilistic quantum cloning (PQC) cannot copy a set of linearly dependent quantum states.In this paper,we show that if incorrect copies are allowed to be produced,linearly dependent quantum states may also be cloned by the PQC.By exploiting this kind of PQC to clone a special set of three linearly dependent quantum states,we derive the upper bound of the maximum confidence measure of a set.An explicit transformation of the maximum confidence measure is presented.
Maximum floodflows in the conterminous United States
Crippen, John R.; Bue, Conrad D.
1977-01-01
Peak floodflows from thousands of observation sites within the conterminous United States were studied to provide a guide for estimating potential maximum floodflows. Data were selected from 883 sites with drainage areas of less than 10,000 square miles (25,900 square kilometers) and were grouped into regional sets. Outstanding floods for each region were plotted on graphs, and envelope curves were computed that offer reasonable limits for estimates of maximum floods. The curves indicate that floods may occur that are two to three times greater than those known for most streams.
Revealing the Maximum Strength in Nanotwinned Copper
Lu, L.; Chen, X.; Huang, Xiaoxu
2009-01-01
The strength of polycrystalline materials increases with decreasing grain size. Below a critical size, smaller grains might lead to softening, as suggested by atomistic simulations. The strongest size should arise at a transition in deformation mechanism from lattice dislocation activities to grain...... boundary–related processes. We investigated the maximum strength of nanotwinned copper samples with different twin thicknesses. We found that the strength increases with decreasing twin thickness, reaching a maximum at 15 nanometers, followed by a softening at smaller values that is accompanied by enhanced...
The Maximum Resource Bin Packing Problem
Boyar, J.; Epstein, L.; Favrholdt, L.M.
2006-01-01
Usually, for bin packing problems, we try to minimize the number of bins used or in the case of the dual bin packing problem, maximize the number or total size of accepted items. This paper presents results for the opposite problems, where we would like to maximize the number of bins used...... algorithms, First-Fit-Increasing and First-Fit-Decreasing for the maximum resource variant of classical bin packing. For the on-line variant, we define maximum resource variants of classical and dual bin packing. For dual bin packing, no on-line algorithm is competitive. For classical bin packing, we find...
Maximum entropy analysis of EGRET data
Pohl, M.; Strong, A.W.
1997-01-01
EGRET data are usually analysed on the basis of the Maximum-Likelihood method \\cite{ma96} in a search for point sources in excess to a model for the background radiation (e.g. \\cite{hu97}). This method depends strongly on the quality of the background model, and thus may have high systematic unce...... uncertainties in region of strong and uncertain background like the Galactic Center region. Here we show images of such regions obtained by the quantified Maximum-Entropy method. We also discuss a possible further use of MEM in the analysis of problematic regions of the sky....
Revealing the Maximum Strength in Nanotwinned Copper
Lu, L.; Chen, X.; Huang, Xiaoxu
2009-01-01
The strength of polycrystalline materials increases with decreasing grain size. Below a critical size, smaller grains might lead to softening, as suggested by atomistic simulations. The strongest size should arise at a transition in deformation mechanism from lattice dislocation activities to grain...... boundary–related processes. We investigated the maximum strength of nanotwinned copper samples with different twin thicknesses. We found that the strength increases with decreasing twin thickness, reaching a maximum at 15 nanometers, followed by a softening at smaller values that is accompanied by enhanced...
Maximum phytoplankton concentrations in the sea
Jackson, G.A.; Kiørboe, Thomas
2008-01-01
A simplification of plankton dynamics using coagulation theory provides predictions of the maximum algal concentration sustainable in aquatic systems. These predictions have previously been tested successfully against results from iron fertilization experiments. We extend the test to data collected...... in the North Atlantic as part of the Bermuda Atlantic Time Series program as well as data collected off Southern California as part of the Southern California Bight Study program. The observed maximum particulate organic carbon and volumetric particle concentrations are consistent with the predictions...
Analysis of Photovoltaic Maximum Power Point Trackers
Veerachary, Mummadi
The photovoltaic generator exhibits a non-linear i-v characteristic and its maximum power point (MPP) varies with solar insolation. An intermediate switch-mode dc-dc converter is required to extract maximum power from the photovoltaic array. In this paper buck, boost and buck-boost topologies are considered and a detailed mathematical analysis, both for continuous and discontinuous inductor current operation, is given for MPP operation. The conditions on the connected load values and duty ratio are derived for achieving the satisfactory maximum power point operation. Further, it is shown that certain load values, falling out of the optimal range, will drive the operating point away from the true maximum power point. Detailed comparison of various topologies for MPPT is given. Selection of the converter topology for a given loading is discussed. Detailed discussion on circuit-oriented model development is given and then MPPT effectiveness of various converter systems is verified through simulations. Proposed theory and analysis is validated through experimental investigations.
On maximum cycle packings in polyhedral graphs
Peter Recht
2014-04-01
Full Text Available This paper addresses upper and lower bounds for the cardinality of a maximum vertex-/edge-disjoint cycle packing in a polyhedral graph G. Bounds on the cardinality of such packings are provided, that depend on the size, the order or the number of faces of G, respectively. Polyhedral graphs are constructed, that attain these bounds.
Hard graphs for the maximum clique problem
Hoede, Cornelis
1988-01-01
The maximum clique problem is one of the NP-complete problems. There are graphs for which a reduction technique exists that transforms the problem for these graphs into one for graphs with specific properties in polynomial time. The resulting graphs do not grow exponentially in order and number. Gra
Maximum Likelihood Estimation of Search Costs
J.L. Moraga-Gonzalez (José Luis); M.R. Wildenbeest (Matthijs)
2006-01-01
textabstractIn a recent paper Hong and Shum (forthcoming) present a structural methodology to estimate search cost distributions. We extend their approach to the case of oligopoly and present a maximum likelihood estimate of the search cost distribution. We apply our method to a data set of online p
Weak Scale From the Maximum Entropy Principle
Hamada, Yuta; Kawana, Kiyoharu
2015-01-01
The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\
Weak scale from the maximum entropy principle
Hamada, Yuta; Kawai, Hikaru; Kawana, Kiyoharu
2015-03-01
The theory of the multiverse and wormholes suggests that the parameters of the Standard Model (SM) are fixed in such a way that the radiation of the S3 universe at the final stage S_rad becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the SM, we can check whether S_rad actually becomes maximum at the observed values. In this paper, we regard S_rad at the final stage as a function of the weak scale (the Higgs expectation value) vh, and show that it becomes maximum around vh = {{O}} (300 GeV) when the dimensionless couplings in the SM, i.e., the Higgs self-coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by vh ˜ T_{BBN}2 / (M_{pl}ye5), where ye is the Yukawa coupling of electron, T_BBN is the temperature at which the Big Bang nucleosynthesis starts, and M_pl is the Planck mass.
Instance Optimality of the Adaptive Maximum Strategy
L. Diening; C. Kreuzer; R. Stevenson
2016-01-01
In this paper, we prove that the standard adaptive finite element method with a (modified) maximum marking strategy is instance optimal for the total error, being the square root of the squared energy error plus the squared oscillation. This result will be derived in the model setting of Poisson’s e
Maximum phonation time: variability and reliability.
Speyer, Renée; Bogaardt, Hans C A; Passos, Valéria Lima; Roodenburg, Nel P H D; Zumach, Anne; Heijnen, Mariëlle A M; Baijens, Laura W J; Fleskens, Stijn J H M; Brunings, Jan W
2010-05-01
The objective of the study was to determine maximum phonation time reliability as a function of the number of trials, days, and raters in dysphonic and control subjects. Two groups of adult subjects participated in this reliability study: a group of outpatients with functional or organic dysphonia versus a group of healthy control subjects matched by age and gender. Over a period of maximally 6 weeks, three video recordings were made of five subjects' maximum phonation time trials. A panel of five experts were responsible for all measurements, including a repeated measurement of the subjects' first recordings. Patients showed significantly shorter maximum phonation times compared with healthy controls (on average, 6.6 seconds shorter). The averaged interclass correlation coefficient (ICC) over all raters per trial for the first day was 0.998. The averaged reliability coefficient per rater and per trial for repeated measurements of the first day's data was 0.997, indicating high intrarater reliability. The mean reliability coefficient per day for one trial was 0.939. When using five trials, the reliability increased to 0.987. The reliability over five trials for a single day was 0.836; for 2 days, 0.911; and for 3 days, 0.935. To conclude, the maximum phonation time has proven to be a highly reliable measure in voice assessment. A single rater is sufficient to provide highly reliable measurements.
Maximum Phonation Time: Variability and Reliability
R. Speyer; H.C.A. Bogaardt; V.L. Passos; N.P.H.D. Roodenburg; A. Zumach; M.A.M. Heijnen; L.W.J. Baijens; S.J.H.M. Fleskens; J.W. Brunings
2010-01-01
The objective of the study was to determine maximum phonation time reliability as a function of the number of trials, days, and raters in dysphonic and control subjects. Two groups of adult subjects participated in this reliability study: a group of outpatients with functional or organic dysphonia v
Maximum likelihood estimation of fractionally cointegrated systems
Lasak, Katarzyna
In this paper we consider a fractionally cointegrated error correction model and investigate asymptotic properties of the maximum likelihood (ML) estimators of the matrix of the cointe- gration relations, the degree of fractional cointegration, the matrix of the speed of adjustment...
Maximum likelihood estimation for integrated diffusion processes
Baltazar-Larios, Fernando; Sørensen, Michael
EM-algorithm to obtain maximum likelihood estimates of the parameters in the diffusion model. As part of the algorithm, we use a recent simple method for approximate simulation of diffusion bridges. In simulation studies for the Ornstein-Uhlenbeck process and the CIR process the proposed method works...
Maximum gain of Yagi-Uda arrays
Bojsen, J.H.; Schjær-Jacobsen, Hans; Nilsson, E.
1971-01-01
Numerical optimisation techniques have been used to find the maximum gain of some specific parasitic arrays. The gain of an array of infinitely thin, equispaced dipoles loaded with arbitrary reactances has been optimised. The results show that standard travelling-wave design methods are not optimum....... Yagi–Uda arrays with equal and unequal spacing have also been optimised with experimental verification....
Cardoso, Humberto Pontes
1990-01-01
The Satelite de Coleta de Dados (SCD) 02 (Data Collection Satellite) has the following characteristics: 115 kg weight, octagonal prism shape, 1 m diameter, and 0.67 m height. Its specified orbit is nearly circular, 700 km altitude, is inclined 25 deg with respect to the equator line, and has 100 min period. The electric power is supplied by eight solar panels installed on the lateral sides of the satellite. The equipment is located on the central (both faces) and lower (internal face) panels. The satellite is spin stabilized and its attitude control is such that during its lifetime, the solar aspect angle will vary between 80 and 100 deg with respect to its spin axis. Two critical cases were selected for thermal control design purposes: Hot case (maximum solar constant, solar aspect angle equal to 100 deg, minimum eclipse time and maximum internal heat dissipation); and a passive thermal design concept was achieved and the maximum and minimum equipment operating temperatures were obtained through a 109 node finite difference mathematical model.
Equatorwards Expansion of Unperturbed, High-Latitude Fast Solar Wind
Dorrian, Gareth; Fallows, Richard; Bisi, Mario
2012-01-01
We use dual-site radio observations of interplanetary scintillation (IPS) with extremely long baselines (ELB) to examine meridional flow characteristics of the ambient fast solar wind at plane-of-sky heliocentric distances of 24-85 solar radii (R\\odot). Our results demonstrate an equatorwards deviation of 3-4{\\deg} in the bulk fast solar wind flow direction over both northern and southern solar hemispheres during different times in the declining phase of Solar Cycle 23.
Precise Determination of the Unperturbed B-8 Neutrino Spectrum
Roger, T.; Buscher, J.; Bastin, B.; Kirsebom, O. S.; Raabe, R.; Alcorta, M.; Aysto, J.; Borge, M. J. G.; Carmona-Gallardo, M.; Cocolios, T. E.; Cruz, J.; Dendooven, P.; Fraile, L. M.; Fynbo, H. O. U.; Galaviz, D.; Gasques, L. R.; Giri, G. S.; Huyse, M.; Hyldegaard, S.; Jungmann, K.; Kruithof, W. L.; Lantz, M.; Perea, A.; Riisager, K.; Saastamoinen, A.; Santra, B.; Shidling, P. D.; Sohani, M.; Sorensen, A. J.; Tengblad, O.; Traykov, E.; van der Hoek, D. J.; Van Duppen, P.; Versolato, O. O.; Wilschut, H. W.
2012-01-01
A measurement of the final state distribution of the B-8 beta decay, obtained by implanting a 8B beam in a double-sided silicon strip detector, is reported here. The present spectrum is consistent with a recent independent precise measurement performed by our collaboration at the IGISOL facility, Jy
Maximum bubble pressure rheology of low molecular mass organogels.
Fei, Pengzhan; Wood, Steven J; Chen, Yan; Cavicchi, Kevin A
2015-01-13
Maximum bubble pressure rheology is used to characterize organogels of 0.25 wt % 12-hydroxystearic acid (12-HSA) in mineral oil, 3 wt % (1,3:2,4) dibenzylidene sorbitol (DBS) in poly(ethylene glycol), and 1 wt % 1,3:2,4-bis(3,4-dimethylbenzylidene) sorbitol (DMDBS) in poly(ethylene glycol). The maximum pressure required to inflate a bubble at the end of capillary inserted in a gel is measured. This pressure is related to the gel modulus in the case of elastic cavitation and the gel modulus and toughness in the case of irreversible fracture. The 12-HSA/mineral oil gels are used to demonstrate that this is a facile technique useful for studying time-dependent gel formation and aging and the thermal transition from a gel to a solution. Comparison is made to both qualitative gel tilting measurements and quantitative oscillatory shear rheology to highlight the utility of this measurement and its complementary nature to oscillatory shear rheology. The DBS and DMDBS demonstrate the generality of this measurement to measure gel transition temperatures.
Model Selection Through Sparse Maximum Likelihood Estimation
Banerjee, Onureena; D'Aspremont, Alexandre
2007-01-01
We consider the problem of estimating the parameters of a Gaussian or binary distribution in such a way that the resulting undirected graphical model is sparse. Our approach is to solve a maximum likelihood problem with an added l_1-norm penalty term. The problem as formulated is convex but the memory requirements and complexity of existing interior point methods are prohibitive for problems with more than tens of nodes. We present two new algorithms for solving problems with at least a thousand nodes in the Gaussian case. Our first algorithm uses block coordinate descent, and can be interpreted as recursive l_1-norm penalized regression. Our second algorithm, based on Nesterov's first order method, yields a complexity estimate with a better dependence on problem size than existing interior point methods. Using a log determinant relaxation of the log partition function (Wainwright & Jordan (2006)), we show that these same algorithms can be used to solve an approximate sparse maximum likelihood problem for...
Maximum-entropy description of animal movement.
Fleming, Chris H; Subaşı, Yiğit; Calabrese, Justin M
2015-03-01
We introduce a class of maximum-entropy states that naturally includes within it all of the major continuous-time stochastic processes that have been applied to animal movement, including Brownian motion, Ornstein-Uhlenbeck motion, integrated Ornstein-Uhlenbeck motion, a recently discovered hybrid of the previous models, and a new model that describes central-place foraging. We are also able to predict a further hierarchy of new models that will emerge as data quality improves to better resolve the underlying continuity of animal movement. Finally, we also show that Langevin equations must obey a fluctuation-dissipation theorem to generate processes that fall from this class of maximum-entropy distributions when the constraints are purely kinematic.
Pareto versus lognormal: a maximum entropy test.
Bee, Marco; Riccaboni, Massimo; Schiavo, Stefano
2011-08-01
It is commonly found that distributions that seem to be lognormal over a broad range change to a power-law (Pareto) distribution for the last few percentiles. The distributions of many physical, natural, and social events (earthquake size, species abundance, income and wealth, as well as file, city, and firm sizes) display this structure. We present a test for the occurrence of power-law tails in statistical distributions based on maximum entropy. This methodology allows one to identify the true data-generating processes even in the case when it is neither lognormal nor Pareto. The maximum entropy approach is then compared with other widely used methods and applied to different levels of aggregation of complex systems. Our results provide support for the theory that distributions with lognormal body and Pareto tail can be generated as mixtures of lognormally distributed units.
Maximum Variance Hashing via Column Generation
Lei Luo
2013-01-01
item search. Recently, a number of data-dependent methods have been developed, reflecting the great potential of learning for hashing. Inspired by the classic nonlinear dimensionality reduction algorithm—maximum variance unfolding, we propose a novel unsupervised hashing method, named maximum variance hashing, in this work. The idea is to maximize the total variance of the hash codes while preserving the local structure of the training data. To solve the derived optimization problem, we propose a column generation algorithm, which directly learns the binary-valued hash functions. We then extend it using anchor graphs to reduce the computational cost. Experiments on large-scale image datasets demonstrate that the proposed method outperforms state-of-the-art hashing methods in many cases.
The Maximum Resource Bin Packing Problem
Boyar, J.; Epstein, L.; Favrholdt, L.M.
2006-01-01
algorithms, First-Fit-Increasing and First-Fit-Decreasing for the maximum resource variant of classical bin packing. For the on-line variant, we define maximum resource variants of classical and dual bin packing. For dual bin packing, no on-line algorithm is competitive. For classical bin packing, we find......Usually, for bin packing problems, we try to minimize the number of bins used or in the case of the dual bin packing problem, maximize the number or total size of accepted items. This paper presents results for the opposite problems, where we would like to maximize the number of bins used...... the competitive ratio of various natural algorithms. We study the general versions of the problems as well as the parameterized versions where there is an upper bound of on the item sizes, for some integer k....
Nonparametric Maximum Entropy Estimation on Information Diagrams
Martin, Elliot A; Meinke, Alexander; Děchtěrenko, Filip; Davidsen, Jörn
2016-01-01
Maximum entropy estimation is of broad interest for inferring properties of systems across many different disciplines. In this work, we significantly extend a technique we previously introduced for estimating the maximum entropy of a set of random discrete variables when conditioning on bivariate mutual informations and univariate entropies. Specifically, we show how to apply the concept to continuous random variables and vastly expand the types of information-theoretic quantities one can condition on. This allows us to establish a number of significant advantages of our approach over existing ones. Not only does our method perform favorably in the undersampled regime, where existing methods fail, but it also can be dramatically less computationally expensive as the cardinality of the variables increases. In addition, we propose a nonparametric formulation of connected informations and give an illustrative example showing how this agrees with the existing parametric formulation in cases of interest. We furthe...
Zipf's law, power laws and maximum entropy
Visser, Matt
2013-04-01
Zipf's law, and power laws in general, have attracted and continue to attract considerable attention in a wide variety of disciplines—from astronomy to demographics to software structure to economics to linguistics to zoology, and even warfare. A recent model of random group formation (RGF) attempts a general explanation of such phenomena based on Jaynes' notion of maximum entropy applied to a particular choice of cost function. In the present paper I argue that the specific cost function used in the RGF model is in fact unnecessarily complicated, and that power laws can be obtained in a much simpler way by applying maximum entropy ideas directly to the Shannon entropy subject only to a single constraint: that the average of the logarithm of the observable quantity is specified.
Zipf's law, power laws, and maximum entropy
Visser, Matt
2012-01-01
Zipf's law, and power laws in general, have attracted and continue to attract considerable attention in a wide variety of disciplines - from astronomy to demographics to economics to linguistics to zoology, and even warfare. A recent model of random group formation [RGF] attempts a general explanation of such phenomena based on Jaynes' notion of maximum entropy applied to a particular choice of cost function. In the present article I argue that the cost function used in the RGF model is in fact unnecessarily complicated, and that power laws can be obtained in a much simpler way by applying maximum entropy ideas directly to the Shannon entropy subject only to a single constraint: that the average of the logarithm of the observable quantity is specified.
Regions of constrained maximum likelihood parameter identifiability
Lee, C.-H.; Herget, C. J.
1975-01-01
This paper considers the parameter identification problem of general discrete-time, nonlinear, multiple-input/multiple-output dynamic systems with Gaussian-white distributed measurement errors. Knowledge of the system parameterization is assumed to be known. Regions of constrained maximum likelihood (CML) parameter identifiability are established. A computation procedure employing interval arithmetic is proposed for finding explicit regions of parameter identifiability for the case of linear systems. It is shown that if the vector of true parameters is locally CML identifiable, then with probability one, the vector of true parameters is a unique maximal point of the maximum likelihood function in the region of parameter identifiability and the CML estimation sequence will converge to the true parameters.
A Maximum Radius for Habitable Planets.
Alibert, Yann
2015-09-01
We compute the maximum radius a planet can have in order to fulfill two constraints that are likely necessary conditions for habitability: 1- surface temperature and pressure compatible with the existence of liquid water, and 2- no ice layer at the bottom of a putative global ocean, that would prevent the operation of the geologic carbon cycle to operate. We demonstrate that, above a given radius, these two constraints cannot be met: in the Super-Earth mass range (1-12 Mearth), the overall maximum that a planet can have varies between 1.8 and 2.3 Rearth. This radius is reduced when considering planets with higher Fe/Si ratios, and taking into account irradiation effects on the structure of the gas envelope.
Maximum Profit Configurations of Commercial Engines
Yiran Chen
2011-01-01
An investigation of commercial engines with finite capacity low- and high-price economic subsystems and a generalized commodity transfer law [n ∝ Δ (P m)] in commodity flow processes, in which effects of the price elasticities of supply and demand are introduced, is presented in this paper. Optimal cycle configurations of commercial engines for maximum profit are obtained by applying optimal control theory. In some special cases, the eventual state—market equilibrium—is solely determined by t...
A stochastic maximum principle via Malliavin calculus
Øksendal, Bernt; Zhou, Xun Yu; Meyer-Brandis, Thilo
2008-01-01
This paper considers a controlled It\\^o-L\\'evy process where the information available to the controller is possibly less than the overall information. All the system coefficients and the objective performance functional are allowed to be random, possibly non-Markovian. Malliavin calculus is employed to derive a maximum principle for the optimal control of such a system where the adjoint process is explicitly expressed.
Tissue radiation response with maximum Tsallis entropy.
Sotolongo-Grau, O; Rodríguez-Pérez, D; Antoranz, J C; Sotolongo-Costa, Oscar
2010-10-08
The expression of survival factors for radiation damaged cells is currently based on probabilistic assumptions and experimentally fitted for each tumor, radiation, and conditions. Here, we show how the simplest of these radiobiological models can be derived from the maximum entropy principle of the classical Boltzmann-Gibbs expression. We extend this derivation using the Tsallis entropy and a cutoff hypothesis, motivated by clinical observations. The obtained expression shows a remarkable agreement with the experimental data found in the literature.
Maximum Estrada Index of Bicyclic Graphs
Wang, Long; Wang, Yi
2012-01-01
Let $G$ be a simple graph of order $n$, let $\\lambda_1(G),\\lambda_2(G),...,\\lambda_n(G)$ be the eigenvalues of the adjacency matrix of $G$. The Esrada index of $G$ is defined as $EE(G)=\\sum_{i=1}^{n}e^{\\lambda_i(G)}$. In this paper we determine the unique graph with maximum Estrada index among bicyclic graphs with fixed order.
Maximum privacy without coherence, zero-error
Leung, Debbie; Yu, Nengkun
2016-09-01
We study the possible difference between the quantum and the private capacities of a quantum channel in the zero-error setting. For a family of channels introduced by Leung et al. [Phys. Rev. Lett. 113, 030512 (2014)], we demonstrate an extreme difference: the zero-error quantum capacity is zero, whereas the zero-error private capacity is maximum given the quantum output dimension.
Automatic maximum entropy spectral reconstruction in NMR.
Mobli, Mehdi; Maciejewski, Mark W; Gryk, Michael R; Hoch, Jeffrey C
2007-10-01
Developments in superconducting magnets, cryogenic probes, isotope labeling strategies, and sophisticated pulse sequences together have enabled the application, in principle, of high-resolution NMR spectroscopy to biomolecular systems approaching 1 megadalton. In practice, however, conventional approaches to NMR that utilize the fast Fourier transform, which require data collected at uniform time intervals, result in prohibitively lengthy data collection times in order to achieve the full resolution afforded by high field magnets. A variety of approaches that involve nonuniform sampling have been proposed, each utilizing a non-Fourier method of spectrum analysis. A very general non-Fourier method that is capable of utilizing data collected using any of the proposed nonuniform sampling strategies is maximum entropy reconstruction. A limiting factor in the adoption of maximum entropy reconstruction in NMR has been the need to specify non-intuitive parameters. Here we describe a fully automated system for maximum entropy reconstruction that requires no user-specified parameters. A web-accessible script generator provides the user interface to the system.
Maximum entropy analysis of cosmic ray composition
Nosek, Dalibor; Vícha, Jakub; Trávníček, Petr; Nosková, Jana
2016-01-01
We focus on the primary composition of cosmic rays with the highest energies that cause extensive air showers in the Earth's atmosphere. A way of examining the two lowest order moments of the sample distribution of the depth of shower maximum is presented. The aim is to show that useful information about the composition of the primary beam can be inferred with limited knowledge we have about processes underlying these observations. In order to describe how the moments of the depth of shower maximum depend on the type of primary particles and their energies, we utilize a superposition model. Using the principle of maximum entropy, we are able to determine what trends in the primary composition are consistent with the input data, while relying on a limited amount of information from shower physics. Some capabilities and limitations of the proposed method are discussed. In order to achieve a realistic description of the primary mass composition, we pay special attention to the choice of the parameters of the sup...
A Maximum Resonant Set of Polyomino Graphs
Zhang Heping
2016-05-01
Full Text Available A polyomino graph P is a connected finite subgraph of the infinite plane grid such that each finite face is surrounded by a regular square of side length one and each edge belongs to at least one square. A dimer covering of P corresponds to a perfect matching. Different dimer coverings can interact via an alternating cycle (or square with respect to them. A set of disjoint squares of P is a resonant set if P has a perfect matching M so that each one of those squares is M-alternating. In this paper, we show that if K is a maximum resonant set of P, then P − K has a unique perfect matching. We further prove that the maximum forcing number of a polyomino graph is equal to the cardinality of a maximum resonant set. This confirms a conjecture of Xu et al. [26]. We also show that if K is a maximal alternating set of P, then P − K has a unique perfect matching.
The maximum rate of mammal evolution
Evans, Alistair R.; Jones, David; Boyer, Alison G.; Brown, James H.; Costa, Daniel P.; Ernest, S. K. Morgan; Fitzgerald, Erich M. G.; Fortelius, Mikael; Gittleman, John L.; Hamilton, Marcus J.; Harding, Larisa E.; Lintulaakso, Kari; Lyons, S. Kathleen; Okie, Jordan G.; Saarinen, Juha J.; Sibly, Richard M.; Smith, Felisa A.; Stephens, Patrick R.; Theodor, Jessica M.; Uhen, Mark D.
2012-03-01
How fast can a mammal evolve from the size of a mouse to the size of an elephant? Achieving such a large transformation calls for major biological reorganization. Thus, the speed at which this occurs has important implications for extensive faunal changes, including adaptive radiations and recovery from mass extinctions. To quantify the pace of large-scale evolution we developed a metric, clade maximum rate, which represents the maximum evolutionary rate of a trait within a clade. We applied this metric to body mass evolution in mammals over the last 70 million years, during which multiple large evolutionary transitions occurred in oceans and on continents and islands. Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. When differences in generation time are considered, we find an exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous-Paleogene (K-Pg) extinction event. Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases. Our findings allow more rigorous comparisons of microevolutionary and macroevolutionary patterns and processes.
Minimal Length, Friedmann Equations and Maximum Density
Awad, Adel
2014-01-01
Inspired by Jacobson's thermodynamic approach[gr-qc/9504004], Cai et al [hep-th/0501055,hep-th/0609128] have shown the emergence of Friedmann equations from the first law of thermodynamics. We extend Akbar--Cai derivation [hep-th/0609128] of Friedmann equations to accommodate a general entropy-area law. Studying the resulted Friedmann equations using a specific entropy-area law, which is motivated by the generalized uncertainty principle (GUP), reveals the existence of a maximum energy density closed to Planck density. Allowing for a general continuous pressure $p(\\rho,a)$ leads to bounded curvature invariants and a general nonsingular evolution. In this case, the maximum energy density is reached in a finite time and there is no cosmological evolution beyond this point which leaves the big bang singularity inaccessible from a spacetime prospective. The existence of maximum energy density and a general nonsingular evolution is independent of the equation of state and the spacial curvature $k$. As an example w...
Maximum saliency bias in binocular fusion
Lu, Yuhao; Stafford, Tom; Fox, Charles
2016-07-01
Subjective experience at any instant consists of a single ("unitary"), coherent interpretation of sense data rather than a "Bayesian blur" of alternatives. However, computation of Bayes-optimal actions has no role for unitary perception, instead being required to integrate over every possible action-percept pair to maximise expected utility. So what is the role of unitary coherent percepts, and how are they computed? Recent work provided objective evidence for non-Bayes-optimal, unitary coherent, perception and action in humans; and further suggested that the percept selected is not the maximum a posteriori percept but is instead affected by utility. The present study uses a binocular fusion task first to reproduce the same effect in a new domain, and second, to test multiple hypotheses about exactly how utility may affect the percept. After accounting for high experimental noise, it finds that both Bayes optimality (maximise expected utility) and the previously proposed maximum-utility hypothesis are outperformed in fitting the data by a modified maximum-salience hypothesis, using unsigned utility magnitudes in place of signed utilities in the bias function.
The maximum rate of mammal evolution
Evans, Alistair R.; Jones, David; Boyer, Alison G.; Brown, James H.; Costa, Daniel P.; Ernest, S. K. Morgan; Fitzgerald, Erich M. G.; Fortelius, Mikael; Gittleman, John L.; Hamilton, Marcus J.; Harding, Larisa E.; Lintulaakso, Kari; Lyons, S. Kathleen; Okie, Jordan G.; Saarinen, Juha J.; Sibly, Richard M.; Smith, Felisa A.; Stephens, Patrick R.; Theodor, Jessica M.; Uhen, Mark D.
2012-01-01
How fast can a mammal evolve from the size of a mouse to the size of an elephant? Achieving such a large transformation calls for major biological reorganization. Thus, the speed at which this occurs has important implications for extensive faunal changes, including adaptive radiations and recovery from mass extinctions. To quantify the pace of large-scale evolution we developed a metric, clade maximum rate, which represents the maximum evolutionary rate of a trait within a clade. We applied this metric to body mass evolution in mammals over the last 70 million years, during which multiple large evolutionary transitions occurred in oceans and on continents and islands. Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. When differences in generation time are considered, we find an exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous–Paleogene (K–Pg) extinction event. Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases. Our findings allow more rigorous comparisons of microevolutionary and macroevolutionary patterns and processes. PMID:22308461
Maximum-biomass prediction of homofermentative Lactobacillus.
Cui, Shumao; Zhao, Jianxin; Liu, Xiaoming; Chen, Yong Q; Zhang, Hao; Chen, Wei
2016-07-01
Fed-batch and pH-controlled cultures have been widely used for industrial production of probiotics. The aim of this study was to systematically investigate the relationship between the maximum biomass of different homofermentative Lactobacillus and lactate accumulation, and to develop a prediction equation for the maximum biomass concentration in such cultures. The accumulation of the end products and the depletion of nutrients by various strains were evaluated. In addition, the minimum inhibitory concentrations (MICs) of acid anions for various strains at pH 7.0 were examined. The lactate concentration at the point of complete inhibition was not significantly different from the MIC of lactate for all of the strains, although the inhibition mechanism of lactate and acetate on Lactobacillus rhamnosus was different from the other strains which were inhibited by the osmotic pressure caused by acid anions at pH 7.0. When the lactate concentration accumulated to the MIC, the strains stopped growing. The maximum biomass was closely related to the biomass yield per unit of lactate produced (YX/P) and the MIC (C) of lactate for different homofermentative Lactobacillus. Based on the experimental data obtained using different homofermentative Lactobacillus, a prediction equation was established as follows: Xmax - X0 = (0.59 ± 0.02)·YX/P·C.
The maximum rate of mammal evolution.
Evans, Alistair R; Jones, David; Boyer, Alison G; Brown, James H; Costa, Daniel P; Ernest, S K Morgan; Fitzgerald, Erich M G; Fortelius, Mikael; Gittleman, John L; Hamilton, Marcus J; Harding, Larisa E; Lintulaakso, Kari; Lyons, S Kathleen; Okie, Jordan G; Saarinen, Juha J; Sibly, Richard M; Smith, Felisa A; Stephens, Patrick R; Theodor, Jessica M; Uhen, Mark D
2012-03-13
How fast can a mammal evolve from the size of a mouse to the size of an elephant? Achieving such a large transformation calls for major biological reorganization. Thus, the speed at which this occurs has important implications for extensive faunal changes, including adaptive radiations and recovery from mass extinctions. To quantify the pace of large-scale evolution we developed a metric, clade maximum rate, which represents the maximum evolutionary rate of a trait within a clade. We applied this metric to body mass evolution in mammals over the last 70 million years, during which multiple large evolutionary transitions occurred in oceans and on continents and islands. Our computations suggest that it took a minimum of 1.6, 5.1, and 10 million generations for terrestrial mammal mass to increase 100-, and 1,000-, and 5,000-fold, respectively. Values for whales were down to half the length (i.e., 1.1, 3, and 5 million generations), perhaps due to the reduced mechanical constraints of living in an aquatic environment. When differences in generation time are considered, we find an exponential increase in maximum mammal body mass during the 35 million years following the Cretaceous-Paleogene (K-Pg) extinction event. Our results also indicate a basic asymmetry in macroevolution: very large decreases (such as extreme insular dwarfism) can happen at more than 10 times the rate of increases. Our findings allow more rigorous comparisons of microevolutionary and macroevolutionary patterns and processes.
Design of materials with extreme thermal expansion using a three-phase topology optimization method
Sigmund, Ole; Torquato, S.
1997-01-01
Composites with extremal or unusual thermal expansion coefficients are designed using a three-phase topology optimization method. The composites are made of two different material phases and a void phase. The topology optimization method consists in finding the distribution of material phases...... materials having maximum directional thermal expansion (thermal actuators), zero isotropic thermal expansion, and negative isotropic thermal expansion. It is shown that materials with effective negative thermal expansion coefficients can be obtained by mixing two phases with positive thermal expansion...
New downshifted maximum in stimulated electromagnetic emission spectra
Sergeev, Evgeny; Grach, Savely
A new spectral maximum in spectra of stimulated electromagnetic emission of the ionosphere (SEE, [1]) was detected in experiments at the SURA facility in 2008 for the pump frequencies f0 4.4-4.5 MHz, most stably for f0 = 4.3 MHz, the lowest possible pump frequency at the SURA facility. The new maximum is situated at frequency shifts ∆f -6 kHz from the pump wave frequency f0 , ∆f = fSEE - f0 , somewhat closer to the f0 than the well known [2,3] Downshifted Maximum in the SEE spectrum at ∆f -9 kHz. The detection and detailed study of the new feature (which we tentatively called the New Downshifted Maximum, NDM) became possible due to high frequency resolution in spectral analysis. The following properties of the NDM are established. (i) The NDM appears in the SEE spectra simultaneously with the DM and UM features after the pump turn on (recall that the less intensive Upshifted Maximum, UM, is situated at ∆f +(6-8) kHz [2,3]). The NDM can't be attributed to 1 DM [4] or Narrow Continuum Maximum (NCM, 2 [5]) SEE features, as well as to splitted DM near gyroharmonics [2]. (ii) The NDM is observed as prominent feature for maximum pump power of the SURA facility P ≈ 120 MW ERP, for which the DM is almost covered by the Broad Continuum SEE feature [2,3]. For P ˜ 30-60 MW ERP the DM and NDM have comparable intensities. For the lesser pump power the DM prevails in the SEE spectrum, while the NDM becomes invisible being covered by the thermal Narrow Continuum feature [2]. (iii) The NDM is exactly symmetrical for the UM relatively to f0 when the former one is observed, although the UM frequency offset increases up to ∆fUM ≈ +9 kHz with a decrease of the pump power up to P ≈ 4 MW ERP. The DM formation in the SEE spectrum is attributed to a three-wave interaction between the upper and lower hybrid waves in the ionosphere, and the lower hybrid frequency ( 7 kHz) determines the frequency offset of the DM high frequency flank [2,6]. The detection of the NDM with
Maximum power operation of interacting molecular motors
Golubeva, Natalia; Imparato, Alberto
2013-01-01
We study the mechanical and thermodynamic properties of different traffic models for kinesin which are relevant in biological and experimental contexts. We find that motor-motor interactions play a fundamental role by enhancing the thermodynamic efficiency at maximum power of the motors......, as compared to the non-interacting system, in a wide range of biologically compatible scenarios. We furthermore consider the case where the motor-motor interaction directly affects the internal chemical cycle and investigate the effect on the system dynamics and thermodynamics....
Maximum a posteriori decoder for digital communications
Altes, Richard A. (Inventor)
1997-01-01
A system and method for decoding by identification of the most likely phase coded signal corresponding to received data. The present invention has particular application to communication with signals that experience spurious random phase perturbations. The generalized estimator-correlator uses a maximum a posteriori (MAP) estimator to generate phase estimates for correlation with incoming data samples and for correlation with mean phases indicative of unique hypothesized signals. The result is a MAP likelihood statistic for each hypothesized transmission, wherein the highest value statistic identifies the transmitted signal.
Kernel-based Maximum Entropy Clustering
JIANG Wei; QU Jiao; LI Benxi
2007-01-01
With the development of Support Vector Machine (SVM),the "kernel method" has been studied in a general way.In this paper,we present a novel Kernel-based Maximum Entropy Clustering algorithm (KMEC).By using mercer kernel functions,the proposed algorithm is firstly map the data from their original space to high dimensional space where the data are expected to be more separable,then perform MEC clustering in the feature space.The experimental results show that the proposed method has better performance in the non-hyperspherical and complex data structure.
The sun and heliosphere at solar maximum.
Smith, E J; Marsden, R G; Balogh, A; Gloeckler, G; Geiss, J; McComas, D J; McKibben, R B; MacDowall, R J; Lanzerotti, L J; Krupp, N; Krueger, H; Landgraf, M
2003-11-14
Recent Ulysses observations from the Sun's equator to the poles reveal fundamental properties of the three-dimensional heliosphere at the maximum in solar activity. The heliospheric magnetic field originates from a magnetic dipole oriented nearly perpendicular to, instead of nearly parallel to, the Sun's rotation axis. Magnetic fields, solar wind, and energetic charged particles from low-latitude sources reach all latitudes, including the polar caps. The very fast high-latitude wind and polar coronal holes disappear and reappear together. Solar wind speed continues to be inversely correlated with coronal temperature. The cosmic ray flux is reduced symmetrically at all latitudes.
Conductivity maximum in a charged colloidal suspension
Bastea, S
2009-01-27
Molecular dynamics simulations of a charged colloidal suspension in the salt-free regime show that the system exhibits an electrical conductivity maximum as a function of colloid charge. We attribute this behavior to two main competing effects: colloid effective charge saturation due to counterion 'condensation' and diffusion slowdown due to the relaxation effect. In agreement with previous observations, we also find that the effective transported charge is larger than the one determined by the Stern layer and suggest that it corresponds to the boundary fluid layer at the surface of the colloidal particles.
Maximum entropy signal restoration with linear programming
Mastin, G.A.; Hanson, R.J.
1988-05-01
Dantzig's bounded-variable method is used to express the maximum entropy restoration problem as a linear programming problem. This is done by approximating the nonlinear objective function with piecewise linear segments, then bounding the variables as a function of the number of segments used. The use of a linear programming approach allows equality constraints found in the traditional Lagrange multiplier method to be relaxed. A robust revised simplex algorithm is used to implement the restoration. Experimental results from 128- and 512-point signal restorations are presented.
COMPARISON BETWEEN FORMULAS OF MAXIMUM SHIP SQUAT
PETRU SERGIU SERBAN
2016-06-01
Full Text Available Ship squat is a combined effect of ship’s draft and trim increase due to ship motion in limited navigation conditions. Over time, researchers conducted tests on models and ships to find a mathematical formula that can define squat. Various forms of calculating squat can be found in the literature. Among those most commonly used are of Barrass, Millward, Eryuzlu or ICORELS. This paper presents a comparison between the squat formulas to see the differences between them and which one provides the most satisfactory results. In this respect a cargo ship at different speeds was considered as a model for maximum squat calculations in canal navigation conditions.
Multi-Channel Maximum Likelihood Pitch Estimation
Christensen, Mads Græsbøll
2012-01-01
In this paper, a method for multi-channel pitch estimation is proposed. The method is a maximum likelihood estimator and is based on a parametric model where the signals in the various channels share the same fundamental frequency but can have different amplitudes, phases, and noise characteristics....... This essentially means that the model allows for different conditions in the various channels, like different signal-to-noise ratios, microphone characteristics and reverberation. Moreover, the method does not assume that a certain array structure is used but rather relies on a more general model and is hence...
Maximum entropy PDF projection: A review
Baggenstoss, Paul M.
2017-06-01
We review maximum entropy (MaxEnt) PDF projection, a method with wide potential applications in statistical inference. The method constructs a sampling distribution for a high-dimensional vector x based on knowing the sampling distribution p(z) of a lower-dimensional feature z = T (x). Under mild conditions, the distribution p(x) having highest possible entropy among all distributions consistent with p(z) may be readily found. Furthermore, the MaxEnt p(x) may be sampled, making the approach useful in Monte Carlo methods. We review the theorem and present a case study in model order selection and classification for handwritten character recognition.
CORA: Emission Line Fitting with Maximum Likelihood
Ness, Jan-Uwe; Wichmann, Rainer
2011-12-01
CORA analyzes emission line spectra with low count numbers and fits them to a line using the maximum likelihood technique. CORA uses a rigorous application of Poisson statistics. From the assumption of Poissonian noise, the software derives the probability for a model of the emission line spectrum to represent the measured spectrum. The likelihood function is used as a criterion for optimizing the parameters of the theoretical spectrum and a fixed point equation is derived allowing an efficient way to obtain line fluxes. CORA has been applied to an X-ray spectrum with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra observatory.
Dynamical maximum entropy approach to flocking
Cavagna, Andrea; Giardina, Irene; Ginelli, Francesco; Mora, Thierry; Piovani, Duccio; Tavarone, Raffaele; Walczak, Aleksandra M.
2014-04-01
We derive a new method to infer from data the out-of-equilibrium alignment dynamics of collectively moving animal groups, by considering the maximum entropy model distribution consistent with temporal and spatial correlations of flight direction. When bird neighborhoods evolve rapidly, this dynamical inference correctly learns the parameters of the model, while a static one relying only on the spatial correlations fails. When neighbors change slowly and the detailed balance is satisfied, we recover the static procedure. We demonstrate the validity of the method on simulated data. The approach is applicable to other systems of active matter.
Zipf's law and maximum sustainable growth
Malevergne, Y; Sornette, D
2010-01-01
Zipf's law states that the number of firms with size greater than S is inversely proportional to S. Most explanations start with Gibrat's rule of proportional growth but require additional constraints. We show that Gibrat's rule, at all firm levels, yields Zipf's law under a balance condition between the effective growth rate of incumbent firms (which includes their possible demise) and the growth rate of investments in entrant firms. Remarkably, Zipf's law is the signature of the long-term optimal allocation of resources that ensures the maximum sustainable growth rate of an economy.
Tripling the maximum imaging depth with third-harmonic generation microscopy.
Yildirim, Murat; Durr, Nicholas; Ben-Yakar, Adela
2015-09-01
The growing interest in performing high-resolution, deep-tissue imaging has galvanized the use of longer excitation wavelengths and three-photon-based techniques in nonlinear imaging modalities. This study presents a threefold improvement in maximum imaging depth of ex vivo porcine vocal folds using third-harmonic generation (THG) microscopy at 1552-nm excitation wavelength compared to two-photon microscopy (TPM) at 776-nm excitation wavelength. The experimental, analytical, and Monte Carlo simulation results reveal that THG improves the maximum imaging depth observed in TPM significantly from 140 to 420 μm in a highly scattered medium, reaching the expected theoretical imaging depth of seven extinction lengths. This value almost doubles the previously reported normalized imaging depths of 3.5 to 4.5 extinction lengths using three-photon-based imaging modalities. Since tissue absorption is substantial at the excitation wavelength of 1552 nm, this study assesses the tissue thermal damage during imaging by obtaining the depth-resolved temperature distribution through a numerical simulation incorporating an experimentally obtained thermal relaxation time (τ). By shuttering the laser for a period of 2τ, the numerical algorithm estimates a maximum temperature increase of ∼2°C at the maximum imaging depth of 420 μm. The paper demonstrates that THG imaging using 1552 nm as an illumination wavelength with effective thermal management proves to be a powerful deep imaging modality for highly scattering and absorbing tissues, such as scarred vocal folds.
Accurate structural correlations from maximum likelihood superpositions.
Douglas L Theobald
2008-02-01
Full Text Available The cores of globular proteins are densely packed, resulting in complicated networks of structural interactions. These interactions in turn give rise to dynamic structural correlations over a wide range of time scales. Accurate analysis of these complex correlations is crucial for understanding biomolecular mechanisms and for relating structure to function. Here we report a highly accurate technique for inferring the major modes of structural correlation in macromolecules using likelihood-based statistical analysis of sets of structures. This method is generally applicable to any ensemble of related molecules, including families of nuclear magnetic resonance (NMR models, different crystal forms of a protein, and structural alignments of homologous proteins, as well as molecular dynamics trajectories. Dominant modes of structural correlation are determined using principal components analysis (PCA of the maximum likelihood estimate of the correlation matrix. The correlations we identify are inherently independent of the statistical uncertainty and dynamic heterogeneity associated with the structural coordinates. We additionally present an easily interpretable method ("PCA plots" for displaying these positional correlations by color-coding them onto a macromolecular structure. Maximum likelihood PCA of structural superpositions, and the structural PCA plots that illustrate the results, will facilitate the accurate determination of dynamic structural correlations analyzed in diverse fields of structural biology.
Maximum entropy production and the fluctuation theorem
Dewar, R C [Unite EPHYSE, INRA Centre de Bordeaux-Aquitaine, BP 81, 33883 Villenave d' Ornon Cedex (France)
2005-05-27
Recently the author used an information theoretical formulation of non-equilibrium statistical mechanics (MaxEnt) to derive the fluctuation theorem (FT) concerning the probability of second law violating phase-space paths. A less rigorous argument leading to the variational principle of maximum entropy production (MEP) was also given. Here a more rigorous and general mathematical derivation of MEP from MaxEnt is presented, and the relationship between MEP and the FT is thereby clarified. Specifically, it is shown that the FT allows a general orthogonality property of maximum information entropy to be extended to entropy production itself, from which MEP then follows. The new derivation highlights MEP and the FT as generic properties of MaxEnt probability distributions involving anti-symmetric constraints, independently of any physical interpretation. Physically, MEP applies to the entropy production of those macroscopic fluxes that are free to vary under the imposed constraints, and corresponds to selection of the most probable macroscopic flux configuration. In special cases MaxEnt also leads to various upper bound transport principles. The relationship between MaxEnt and previous theories of irreversible processes due to Onsager, Prigogine and Ziegler is also clarified in the light of these results. (letter to the editor)
Thermodynamic hardness and the maximum hardness principle
Franco-Pérez, Marco; Gázquez, José L.; Ayers, Paul W.; Vela, Alberto
2017-08-01
An alternative definition of hardness (called the thermodynamic hardness) within the grand canonical ensemble formalism is proposed in terms of the partial derivative of the electronic chemical potential with respect to the thermodynamic chemical potential of the reservoir, keeping the temperature and the external potential constant. This temperature dependent definition may be interpreted as a measure of the propensity of a system to go through a charge transfer process when it interacts with other species, and thus it keeps the philosophy of the original definition. When the derivative is expressed in terms of the three-state ensemble model, in the regime of low temperatures and up to temperatures of chemical interest, one finds that for zero fractional charge, the thermodynamic hardness is proportional to T-1(I -A ) , where I is the first ionization potential, A is the electron affinity, and T is the temperature. However, the thermodynamic hardness is nearly zero when the fractional charge is different from zero. Thus, through the present definition, one avoids the presence of the Dirac delta function. We show that the chemical hardness defined in this way provides meaningful and discernible information about the hardness properties of a chemical species exhibiting integer or a fractional average number of electrons, and this analysis allowed us to establish a link between the maximum possible value of the hardness here defined, with the minimum softness principle, showing that both principles are related to minimum fractional charge and maximum stability conditions.
Maximum Likelihood Analysis in the PEN Experiment
Lehman, Martin
2013-10-01
The experimental determination of the π+ -->e+ ν (γ) decay branching ratio currently provides the most accurate test of lepton universality. The PEN experiment at PSI, Switzerland, aims to improve the present world average experimental precision of 3 . 3 ×10-3 to 5 ×10-4 using a stopped beam approach. During runs in 2008-10, PEN has acquired over 2 ×107 πe 2 events. The experiment includes active beam detectors (degrader, mini TPC, target), central MWPC tracking with plastic scintillator hodoscopes, and a spherical pure CsI electromagnetic shower calorimeter. The final branching ratio will be calculated using a maximum likelihood analysis. This analysis assigns each event a probability for 5 processes (π+ -->e+ ν , π+ -->μ+ ν , decay-in-flight, pile-up, and hadronic events) using Monte Carlo verified probability distribution functions of our observables (energies, times, etc). A progress report on the PEN maximum likelihood analysis will be presented. Work supported by NSF grant PHY-0970013.
Lake Basin Fetch and Maximum Length/Width
Minnesota Department of Natural Resources — Linear features representing the Fetch, Maximum Length and Maximum Width of a lake basin. Fetch, maximum length and average width are calcuated from the lake polygon...
d’Ambrosio Alfano, Francesca Romana; Olesen, Bjarne W.; Palella, Boris Igor;
2014-01-01
Thermal comfort is one of the most important aspects of the indoor environmental quality due to its effects on well-being, people's performance and building energy requirements. Its attainment is not an easy task requiring advanced design and operation of building and HVAC systems, taking...... into account all parameters involved. Even though thermal comfort fundamentals are consolidated topics for more than forty years, often designers seem to ignore or apply them in a wrong way. Design input values from standards are often considered as universal values rather than recommended values to be used...... under specific conditions. At operation level, only few variables are taken into account with unpredictable effects on the assessment of comfort indices. In this paper, the main criteria for the design and assessment of thermal comfort are discussed in order to help building and HVAC systems designers...
Maximum entropy principle and texture formation
Arminjon, M; Arminjon, Mayeul; Imbault, Didier
2006-01-01
The macro-to-micro transition in a heterogeneous material is envisaged as the selection of a probability distribution by the Principle of Maximum Entropy (MAXENT). The material is made of constituents, e.g. given crystal orientations. Each constituent is itself made of a large number of elementary constituents. The relevant probability is the volume fraction of the elementary constituents that belong to a given constituent and undergo a given stimulus. Assuming only obvious constraints in MAXENT means describing a maximally disordered material. This is proved to have the same average stimulus in each constituent. By adding a constraint in MAXENT, a new model, potentially interesting e.g. for texture prediction, is obtained.
MLDS: Maximum Likelihood Difference Scaling in R
Kenneth Knoblauch
2008-01-01
Full Text Available The MLDS package in the R programming language can be used to estimate perceptual scales based on the results of psychophysical experiments using the method of difference scaling. In a difference scaling experiment, observers compare two supra-threshold differences (a,b and (c,d on each trial. The approach is based on a stochastic model of how the observer decides which perceptual difference (or interval (a,b or (c,d is greater, and the parameters of the model are estimated using a maximum likelihood criterion. We also propose a method to test the model by evaluating the self-consistency of the estimated scale. The package includes an example in which an observer judges the differences in correlation between scatterplots. The example may be readily adapted to estimate perceptual scales for arbitrary physical continua.
Maximum Profit Configurations of Commercial Engines
Yiran Chen
2011-06-01
Full Text Available An investigation of commercial engines with finite capacity low- and high-price economic subsystems and a generalized commodity transfer law [n ∝ Δ (P m] in commodity flow processes, in which effects of the price elasticities of supply and demand are introduced, is presented in this paper. Optimal cycle configurations of commercial engines for maximum profit are obtained by applying optimal control theory. In some special cases, the eventual state—market equilibrium—is solely determined by the initial conditions and the inherent characteristics of two subsystems; while the different ways of transfer affect the model in respects of the specific forms of the paths of prices and the instantaneous commodity flow, i.e., the optimal configuration.
Maximum Segment Sum, Monadically (distilled tutorial
Jeremy Gibbons
2011-09-01
Full Text Available The maximum segment sum problem is to compute, given a list of integers, the largest of the sums of the contiguous segments of that list. This problem specification maps directly onto a cubic-time algorithm; however, there is a very elegant linear-time solution too. The problem is a classic exercise in the mathematics of program construction, illustrating important principles such as calculational development, pointfree reasoning, algebraic structure, and datatype-genericity. Here, we take a sideways look at the datatype-generic version of the problem in terms of monadic functional programming, instead of the traditional relational approach; the presentation is tutorial in style, and leavened with exercises for the reader.
Maximum Information and Quantum Prediction Algorithms
McElwaine, J N
1997-01-01
This paper describes an algorithm for selecting a consistent set within the consistent histories approach to quantum mechanics and investigates its properties. The algorithm uses a maximum information principle to select from among the consistent sets formed by projections defined by the Schmidt decomposition. The algorithm unconditionally predicts the possible events in closed quantum systems and ascribes probabilities to these events. A simple spin model is described and a complete classification of all exactly consistent sets of histories formed from Schmidt projections in the model is proved. This result is used to show that for this example the algorithm selects a physically realistic set. Other tentative suggestions in the literature for set selection algorithms using ideas from information theory are discussed.
Maximum process problems in optimal control theory
Goran Peskir
2005-01-01
Full Text Available Given a standard Brownian motion (Btt≥0 and the equation of motion dXt=vtdt+2dBt, we set St=max0≤s≤tXs and consider the optimal control problem supvE(Sτ−Cτ, where c>0 and the supremum is taken over all admissible controls v satisfying vt∈[μ0,μ1] for all t up to τ=inf{t>0|Xt∉(ℓ0,ℓ1} with μ0g∗(St, where s↦g∗(s is a switching curve that is determined explicitly (as the unique solution to a nonlinear differential equation. The solution found demonstrates that the problem formulations based on a maximum functional can be successfully included in optimal control theory (calculus of variations in addition to the classic problem formulations due to Lagrange, Mayer, and Bolza.
Maximum Spectral Luminous Efficacy of White Light
Murphy, T W
2013-01-01
As lighting efficiency improves, it is useful to understand the theoretical limits to luminous efficacy for light that we perceive as white. Independent of the efficiency with which photons are generated, there exists a spectrally-imposed limit to the luminous efficacy of any source of photons. We find that, depending on the acceptable bandpass and---to a lesser extent---the color temperature of the light, the ideal white light source achieves a spectral luminous efficacy of 250--370 lm/W. This is consistent with previous calculations, but here we explore the maximum luminous efficacy as a function of photopic sensitivity threshold, color temperature, and color rendering index; deriving peak performance as a function of all three parameters. We also present example experimental spectra from a variety of light sources, quantifying the intrinsic efficacy of their spectral distributions.
Maximum entropy model for business cycle synchronization
Xi, Ning; Muneepeerakul, Rachata; Azaele, Sandro; Wang, Yougui
2014-11-01
The global economy is a complex dynamical system, whose cyclical fluctuations can mainly be characterized by simultaneous recessions or expansions of major economies. Thus, the researches on the synchronization phenomenon are key to understanding and controlling the dynamics of the global economy. Based on a pairwise maximum entropy model, we analyze the business cycle synchronization of the G7 economic system. We obtain a pairwise-interaction network, which exhibits certain clustering structure and accounts for 45% of the entire structure of the interactions within the G7 system. We also find that the pairwise interactions become increasingly inadequate in capturing the synchronization as the size of economic system grows. Thus, higher-order interactions must be taken into account when investigating behaviors of large economic systems.
Quantum gravity momentum representation and maximum energy
Moffat, J. W.
2016-11-01
We use the idea of the symmetry between the spacetime coordinates xμ and the energy-momentum pμ in quantum theory to construct a momentum space quantum gravity geometry with a metric sμν and a curvature tensor Pλ μνρ. For a closed maximally symmetric momentum space with a constant 3-curvature, the volume of the p-space admits a cutoff with an invariant maximum momentum a. A Wheeler-DeWitt-type wave equation is obtained in the momentum space representation. The vacuum energy density and the self-energy of a charged particle are shown to be finite, and modifications of the electromagnetic radiation density and the entropy density of a system of particles occur for high frequencies.
Video segmentation using Maximum Entropy Model
QIN Li-juan; ZHUANG Yue-ting; PAN Yun-he; WU Fei
2005-01-01
Detecting objects of interest from a video sequence is a fundamental and critical task in automated visual surveillance.Most current approaches only focus on discriminating moving objects by background subtraction whether or not the objects of interest can be moving or stationary. In this paper, we propose layers segmentation to detect both moving and stationary target objects from surveillance video. We extend the Maximum Entropy (ME) statistical model to segment layers with features, which are collected by constructing a codebook with a set of codewords for each pixel. We also indicate how the training models are used for the discrimination of target objects in surveillance video. Our experimental results are presented in terms of the success rate and the segmenting precision.
Maximum-power-point tracking control of solar heating system
Huang, Bin-Juine
2012-11-01
The present study developed a maximum-power point tracking control (MPPT) technology for solar heating system to minimize the pumping power consumption at an optimal heat collection. The net solar energy gain Q net (=Q s-W p/η e) was experimentally found to be the cost function for MPPT with maximum point. The feedback tracking control system was developed to track the optimal Q net (denoted Q max). A tracking filter which was derived from the thermal analytical model of the solar heating system was used to determine the instantaneous tracking target Q max(t). The system transfer-function model of solar heating system was also derived experimentally using a step response test and used in the design of tracking feedback control system. The PI controller was designed for a tracking target Q max(t) with a quadratic time function. The MPPT control system was implemented using a microprocessor-based controller and the test results show good tracking performance with small tracking errors. It is seen that the average mass flow rate for the specific test periods in five different days is between 18.1 and 22.9kg/min with average pumping power between 77 and 140W, which is greatly reduced as compared to the standard flow rate at 31kg/min and pumping power 450W which is based on the flow rate 0.02kg/sm 2 defined in the ANSI/ASHRAE 93-1986 Standard and the total collector area 25.9m 2. The average net solar heat collected Q net is between 8.62 and 14.1kW depending on weather condition. The MPPT control of solar heating system has been verified to be able to minimize the pumping energy consumption with optimal solar heat collection. © 2012 Elsevier Ltd.
Thermal fatigue. Fluid-structure interaction at thermal mixing events
Schuler, X.; Herter, K.H.; Moogk, S. [Stuttgart Univ. (Germany). MPA; Laurien, E.; Kloeren, D.; Kulenovic, R.; Kuschewski, M. [Stuttgart Univ. (Germany). Inst. of Nuclear Technology and Energy Systems
2012-07-01
In the framework of the network research project ''Thermal Fatigue - Basics of the system-, outflow- and material-characteristics of piping under thermal fatigue'' funded by the German Federal Ministry of Education and Research (BMBF) fundamental numerical and experimental investigations on the material behaviour under transient thermal-mechanical stress conditions (high cycle fatigue - HCF) are carried out. The project's background and its network of scientific working groups with their individual working tasks are briefly introduced. The main focus is especially on the joint research tasks within the sub-projects of MPA and IKE which are dealing with thermal mixing of flows in a T-junction configuration and the fluidstructure- interactions (FSI). Therefore, experiments were performed with the newly established FSI test facility at MPA which enables single-phase flow experiments of water in typical power plant piping diameters (DN40 and DN80) at high pressure (maximum 75 bar) and temperatures (maximum 280 C). The experimental results serve as validation data base for numerical modelling of thermal flow mixing by means of thermo-fluid dynamics simulations applying CFD techniques and carried out by IKE as well as for modelling of thermal and mechanical loads of the piping structure by structural mechanics simulations with FEM methods which are executed by MPA. The FSI test facility will be described inclusively the applied measurement techniques, e. g. in particular the novel near-wall LED-induced Fluorescence method for non-intrusive flow temperature measurements. First experimental data and numerical results from CFD and FEM simulations of the thermal mixing of flows in the T-junction are presented.
Craps, Ben; Nguyen, Kévin
2016-01-01
Matrix quantum mechanics offers an attractive environment for discussing gravitational holography, in which both sides of the holographic duality are well-defined. Similarly to higher-dimensional implementations of holography, collapsing shell solutions in the gravitational bulk correspond in this setting to thermalization processes in the dual quantum mechanical theory. We construct an explicit, fully nonlinear supergravity solution describing a generic collapsing dilaton shell, specify the holographic renormalization prescriptions necessary for computing the relevant boundary observables, and apply them to evaluating thermalizing two-point correlation functions in the dual matrix theory.
Evaluation of pliers' grip spans in the maximum gripping task and sub-maximum cutting task.
Kim, Dae-Min; Kong, Yong-Ku
2016-12-01
A total of 25 males participated to investigate the effects of the grip spans of pliers on the total grip force, individual finger forces and muscle activities in the maximum gripping task and wire-cutting tasks. In the maximum gripping task, results showed that the 50-mm grip span had significantly higher total grip strength than the other grip spans. In the cutting task, the 50-mm grip span also showed significantly higher grip strength than the 65-mm and 80-mm grip spans, whereas the muscle activities showed a higher value at 80-mm grip span. The ratios of cutting force to maximum grip strength were also investigated. Ratios of 30.3%, 31.3% and 41.3% were obtained by grip spans of 50-mm, 65-mm, and 80-mm, respectively. Thus, the 50-mm grip span for pliers might be recommended to provide maximum exertion in gripping tasks, as well as lower maximum-cutting force ratios in the cutting tasks.
Cosmic shear measurement with maximum likelihood and maximum a posteriori inference
Hall, Alex
2016-01-01
We investigate the problem of noise bias in maximum likelihood and maximum a posteriori estimators for cosmic shear. We derive the leading and next-to-leading order biases and compute them in the context of galaxy ellipticity measurements, extending previous work on maximum likelihood inference for weak lensing. We show that a large part of the bias on these point estimators can be removed using information already contained in the likelihood when a galaxy model is specified, without the need for external calibration. We test these bias-corrected estimators on simulated galaxy images similar to those expected from planned space-based weak lensing surveys, with very promising results. We find that the introduction of an intrinsic shape prior mitigates noise bias, such that the maximum a posteriori estimate can be made less biased than the maximum likelihood estimate. Second-order terms offer a check on the convergence of the estimators, but are largely sub-dominant. We show how biases propagate to shear estima...
Thermal adaptation and phosphorus shape thermal performance in an assemblage of rainforest ants.
Kaspari, Michael; Clay, Natalie A; Lucas, Jane; Revzen, Shai; Kay, Adam; Yanoviak, Stephen P
2016-04-01
We studied the Thermal Performance Curves (TPCs) of 87 species of rainforest ants and found support for both the Thermal Adaptation and Phosphorus-Tolerance hypotheses. TPCs relate a fitness proxy (here, worker speed) to environmental temperature. Thermal Adaptation posits that thermal generalists (ants with flatter, broader TPCs) are favored in the hotter, more variable tropical canopy compared to the cooler, less variable litter below. As predicted, species nesting in the forest canopy 1) had running speeds less sensitive to temperature; 2) ran over a greater range of temperatures; and 3) ran at lower maximum speeds. Tradeoffs between tolerance and maximum performance are often invoked for constraining the evolution of thermal generalists. There was no evidence that ant species traded off thermal tolerance for maximum speed, however. Phosphorus-Tolerance is a second mechanism for generating ectotherms able to tolerate thermal extremes. It posits that ants active at high temperatures invest in P-rich machinery to buffer their metabolism against thermal extremes. Phosphorus content in ant tissue varied three-fold, and as predicted, temperature sensitivity was lower and thermal range was higher in P-rich species. Combined, we show how the vertical distribution of hot and variable vs. cooler and stable microclimates in a single forest contribute to a diversity of TPCs and suggest that a widely varying P stoichiometry among these ants may drive some of these differences.
Thermal Hardware for the Thermal Analyst
Steinfeld, David
2015-01-01
The presentation will be given at the 26th Annual Thermal Fluids Analysis Workshop (TFAWS 2015) hosted by the Goddard Space Flight Center (GSFC) Thermal Engineering Branch (Code 545). NCTS 21070-1. Most Thermal analysts do not have a good background into the hardware which thermally controls the spacecraft they design. SINDA and Thermal Desktop models are nice, but knowing how this applies to the actual thermal hardware (heaters, thermostats, thermistors, MLI blanketing, optical coatings, etc...) is just as important. The course will delve into the thermal hardware and their application techniques on actual spacecraft. Knowledge of how thermal hardware is used and applied will make a thermal analyst a better engineer.
Investigation of Maximum Power Point Tracking for Thermoelectric Generators
Phillip, Navneesh; Maganga, Othman; Burnham, Keith J.; Ellis, Mark A.; Robinson, Simon; Dunn, Julian; Rouaud, Cedric
2013-07-01
In this paper, a thermoelectric generator (TEG) model is developed as a tool for investigating optimized maximum power point tracking (MPPT) algorithms for TEG systems within automotive exhaust heat energy recovery applications. The model comprises three main subsystems that make up the TEG system: the heat exchanger, thermoelectric material, and power conditioning unit (PCU). In this study, two MPPT algorithms known as the perturb and observe (P&O) algorithm and extremum seeking control (ESC) are investigated. A synchronous buck-boost converter is implemented as the preferred DC-DC converter topology, and together with the MPPT algorithm completes the PCU architecture. The process of developing the subsystems is discussed, and the advantage of using the MPPT controller is demonstrated. The simulation results demonstrate that the ESC algorithm implemented in combination with a synchronous buck-boost converter achieves favorable power outputs for TEG systems. The appropriateness is by virtue of greater responsiveness to changes in the system's thermal conditions and hence the electrical potential difference generated in comparison with the P&O algorithm. The MATLAB/Simulink environment is used for simulation of the TEG system and comparison of the investigated control strategies.
20 CFR 211.14 - Maximum creditable compensation.
2010-04-01
... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Maximum creditable compensation. 211.14... CREDITABLE RAILROAD COMPENSATION § 211.14 Maximum creditable compensation. Maximum creditable compensation... Employment Accounts shall notify each employer of the amount of maximum creditable compensation applicable...
49 CFR 230.24 - Maximum allowable stress.
2010-10-01
... 49 Transportation 4 2010-10-01 2010-10-01 false Maximum allowable stress. 230.24 Section 230.24... Allowable Stress § 230.24 Maximum allowable stress. (a) Maximum allowable stress value. The maximum allowable stress value on any component of a steam locomotive boiler shall not exceed 1/4 of the ultimate...
Theoretical Estimate of Maximum Possible Nuclear Explosion
Bethe, H. A.
1950-01-31
The maximum nuclear accident which could occur in a Na-cooled, Be moderated, Pu and power producing reactor is estimated theoretically. (T.R.H.) 2O82 Results of nuclear calculations for a variety of compositions of fast, heterogeneous, sodium-cooled, U-235-fueled, plutonium- and power-producing reactors are reported. Core compositions typical of plate-, pin-, or wire-type fuel elements and with uranium as metal, alloy, and oxide were considered. These compositions included atom ratios in the following range: U-23B to U-235 from 2 to 8; sodium to U-235 from 1.5 to 12; iron to U-235 from 5 to 18; and vanadium to U-235 from 11 to 33. Calculations were performed to determine the effect of lead and iron reflectors between the core and blanket. Both natural and depleted uranium were evaluated as the blanket fertile material. Reactors were compared on a basis of conversion ratio, specific power, and the product of both. The calculated results are in general agreement with the experimental results from fast reactor assemblies. An analysis of the effect of new cross-section values as they became available is included. (auth)
Proposed principles of maximum local entropy production.
Ross, John; Corlan, Alexandru D; Müller, Stefan C
2012-07-12
Articles have appeared that rely on the application of some form of "maximum local entropy production principle" (MEPP). This is usually an optimization principle that is supposed to compensate for the lack of structural information and measurements about complex systems, even systems as complex and as little characterized as the whole biosphere or the atmosphere of the Earth or even of less known bodies in the solar system. We select a number of claims from a few well-known papers that advocate this principle and we show that they are in error with the help of simple examples of well-known chemical and physical systems. These erroneous interpretations can be attributed to ignoring well-established and verified theoretical results such as (1) entropy does not necessarily increase in nonisolated systems, such as "local" subsystems; (2) macroscopic systems, as described by classical physics, are in general intrinsically deterministic-there are no "choices" in their evolution to be selected by using supplementary principles; (3) macroscopic deterministic systems are predictable to the extent to which their state and structure is sufficiently well-known; usually they are not sufficiently known, and probabilistic methods need to be employed for their prediction; and (4) there is no causal relationship between the thermodynamic constraints and the kinetics of reaction systems. In conclusion, any predictions based on MEPP-like principles should not be considered scientifically founded.
Maximum entropy production and plant optimization theories.
Dewar, Roderick C
2010-05-12
Plant ecologists have proposed a variety of optimization theories to explain the adaptive behaviour and evolution of plants from the perspective of natural selection ('survival of the fittest'). Optimization theories identify some objective function--such as shoot or canopy photosynthesis, or growth rate--which is maximized with respect to one or more plant functional traits. However, the link between these objective functions and individual plant fitness is seldom quantified and there remains some uncertainty about the most appropriate choice of objective function to use. Here, plants are viewed from an alternative thermodynamic perspective, as members of a wider class of non-equilibrium systems for which maximum entropy production (MEP) has been proposed as a common theoretical principle. I show how MEP unifies different plant optimization theories that have been proposed previously on the basis of ad hoc measures of individual fitness--the different objective functions of these theories emerge as examples of entropy production on different spatio-temporal scales. The proposed statistical explanation of MEP, that states of MEP are by far the most probable ones, suggests a new and extended paradigm for biological evolution--'survival of the likeliest'--which applies from biomacromolecules to ecosystems, not just to individuals.
Maximum likelihood continuity mapping for fraud detection
Hogden, J.
1997-05-01
The author describes a novel time-series analysis technique called maximum likelihood continuity mapping (MALCOM), and focuses on one application of MALCOM: detecting fraud in medical insurance claims. Given a training data set composed of typical sequences, MALCOM creates a stochastic model of sequence generation, called a continuity map (CM). A CM maximizes the probability of sequences in the training set given the model constraints, CMs can be used to estimate the likelihood of sequences not found in the training set, enabling anomaly detection and sequence prediction--important aspects of data mining. Since MALCOM can be used on sequences of categorical data (e.g., sequences of words) as well as real valued data, MALCOM is also a potential replacement for database search tools such as N-gram analysis. In a recent experiment, MALCOM was used to evaluate the likelihood of patient medical histories, where ``medical history`` is used to mean the sequence of medical procedures performed on a patient. Physicians whose patients had anomalous medical histories (according to MALCOM) were evaluated for fraud by an independent agency. Of the small sample (12 physicians) that has been evaluated, 92% have been determined fraudulent or abusive. Despite the small sample, these results are encouraging.
Maximum life spiral bevel reduction design
Savage, M.; Prasanna, M. G.; Coe, H. H.
1992-07-01
Optimization is applied to the design of a spiral bevel gear reduction for maximum life at a given size. A modified feasible directions search algorithm permits a wide variety of inequality constraints and exact design requirements to be met with low sensitivity to initial values. Gear tooth bending strength and minimum contact ratio under load are included in the active constraints. The optimal design of the spiral bevel gear reduction includes the selection of bearing and shaft proportions in addition to gear mesh parameters. System life is maximized subject to a fixed back-cone distance of the spiral bevel gear set for a specified speed ratio, shaft angle, input torque, and power. Significant parameters in the design are: the spiral angle, the pressure angle, the numbers of teeth on the pinion and gear, and the location and size of the four support bearings. Interpolated polynomials expand the discrete bearing properties and proportions into continuous variables for gradient optimization. After finding the continuous optimum, a designer can analyze near optimal designs for comparison and selection. Design examples show the influence of the bearing lives on the gear parameters in the optimal configurations. For a fixed back-cone distance, optimal designs with larger shaft angles have larger service lives.
CORA - emission line fitting with Maximum Likelihood
Ness, J.-U.; Wichmann, R.
2002-07-01
The advent of pipeline-processed data both from space- and ground-based observatories often disposes of the need of full-fledged data reduction software with its associated steep learning curve. In many cases, a simple tool doing just one task, and doing it right, is all one wishes. In this spirit we introduce CORA, a line fitting tool based on the maximum likelihood technique, which has been developed for the analysis of emission line spectra with low count numbers and has successfully been used in several publications. CORA uses a rigorous application of Poisson statistics. From the assumption of Poissonian noise we derive the probability for a model of the emission line spectrum to represent the measured spectrum. The likelihood function is used as a criterion for optimizing the parameters of the theoretical spectrum and a fixed point equation is derived allowing an efficient way to obtain line fluxes. As an example we demonstrate the functionality of the program with an X-ray spectrum of Capella obtained with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra observatory and choose the analysis of the Ne IX triplet around 13.5 Å.
Finding maximum JPEG image block code size
Lakhani, Gopal
2012-07-01
We present a study of JPEG baseline coding. It aims to determine the minimum storage needed to buffer the JPEG Huffman code bits of 8-bit image blocks. Since DC is coded separately, and the encoder represents each AC coefficient by a pair of run-length/AC coefficient level, the net problem is to perform an efficient search for the optimal run-level pair sequence. We formulate it as a two-dimensional, nonlinear, integer programming problem and solve it using a branch-and-bound based search method. We derive two types of constraints to prune the search space. The first one is given as an upper-bound for the sum of squares of AC coefficients of a block, and it is used to discard sequences that cannot represent valid DCT blocks. The second type constraints are based on some interesting properties of the Huffman code table, and these are used to prune sequences that cannot be part of optimal solutions. Our main result is that if the default JPEG compression setting is used, space of minimum of 346 bits and maximum of 433 bits is sufficient to buffer the AC code bits of 8-bit image blocks. Our implementation also pruned the search space extremely well; the first constraint reduced the initial search space of 4 nodes down to less than 2 nodes, and the second set of constraints reduced it further by 97.8%.
Maximum likelihood estimates of pairwise rearrangement distances.
Serdoz, Stuart; Egri-Nagy, Attila; Sumner, Jeremy; Holland, Barbara R; Jarvis, Peter D; Tanaka, Mark M; Francis, Andrew R
2017-06-21
Accurate estimation of evolutionary distances between taxa is important for many phylogenetic reconstruction methods. Distances can be estimated using a range of different evolutionary models, from single nucleotide polymorphisms to large-scale genome rearrangements. Corresponding corrections for genome rearrangement distances fall into 3 categories: Empirical computational studies, Bayesian/MCMC approaches, and combinatorial approaches. Here, we introduce a maximum likelihood estimator for the inversion distance between a pair of genomes, using a group-theoretic approach to modelling inversions introduced recently. This MLE functions as a corrected distance: in particular, we show that because of the way sequences of inversions interact with each other, it is quite possible for minimal distance and MLE distance to differently order the distances of two genomes from a third. The second aspect tackles the problem of accounting for the symmetries of circular arrangements. While, generally, a frame of reference is locked, and all computation made accordingly, this work incorporates the action of the dihedral group so that distance estimates are free from any a priori frame of reference. The philosophy of accounting for symmetries can be applied to any existing correction method, for which examples are offered. Copyright © 2017 Elsevier Ltd. All rights reserved.
Boedeker, Peter
2017-01-01
Hierarchical linear modeling (HLM) is a useful tool when analyzing data collected from groups. There are many decisions to be made when constructing and estimating a model in HLM including which estimation technique to use. Three of the estimation techniques available when analyzing data with HLM are maximum likelihood, restricted maximum…
Design of materials with extreme thermal expansion using a three-phase topology optimization method
Sigmund, Ole; Torquato, S.
1997-01-01
We show how composites with extremal or unusual thermal expansion coefficients can be designed using a numerical topology optimization method. The composites are composed of two different material phases and void. The optimization method is illustrated by designing materials having maximum thermal...... expansion, zero thermal expansion, and negative thermal expansion. Assuming linear elasticity, it is shown that materials with effective negative thermal expansion coefficients can be obtained by mixing two phases with positive thermal expansion coefficients and void. We also show...
Recommended Maximum Temperature For Mars Returned Samples
Beaty, D. W.; McSween, H. Y.; Czaja, A. D.; Goreva, Y. S.; Hausrath, E.; Herd, C. D. K.; Humayun, M.; McCubbin, F. M.; McLennan, S. M.; Hays, L. E.
2016-01-01
The Returned Sample Science Board (RSSB) was established in 2015 by NASA to provide expertise from the planetary sample community to the Mars 2020 Project. The RSSB's first task was to address the effect of heating during acquisition and storage of samples on scientific investigations that could be expected to be conducted if the samples are returned to Earth. Sample heating may cause changes that could ad-versely affect scientific investigations. Previous studies of temperature requirements for returned mar-tian samples fall within a wide range (-73 to 50 degrees Centigrade) and, for mission concepts that have a life detection component, the recommended threshold was less than or equal to -20 degrees Centigrade. The RSSB was asked by the Mars 2020 project to determine whether or not a temperature requirement was needed within the range of 30 to 70 degrees Centigrade. There are eight expected temperature regimes to which the samples could be exposed, from the moment that they are drilled until they are placed into a temperature-controlled environment on Earth. Two of those - heating during sample acquisition (drilling) and heating while cached on the Martian surface - potentially subject samples to the highest temperatures. The RSSB focused on the upper temperature limit that Mars samples should be allowed to reach. We considered 11 scientific investigations where thermal excursions may have an adverse effect on the science outcome. Those are: (T-1) organic geochemistry, (T-2) stable isotope geochemistry, (T-3) prevention of mineral hydration/dehydration and phase transformation, (T-4) retention of water, (T-5) characterization of amorphous materials, (T-6) putative Martian organisms, (T-7) oxidation/reduction reactions, (T-8) (sup 4) He thermochronometry, (T-9) radiometric dating using fission, cosmic-ray or solar-flare tracks, (T-10) analyses of trapped gasses, and (T-11) magnetic studies.
Maximum likelihood molecular clock comb: analytic solutions.
Chor, Benny; Khetan, Amit; Snir, Sagi
2006-04-01
Maximum likelihood (ML) is increasingly used as an optimality criterion for selecting evolutionary trees, but finding the global optimum is a hard computational task. Because no general analytic solution is known, numeric techniques such as hill climbing or expectation maximization (EM), are used in order to find optimal parameters for a given tree. So far, analytic solutions were derived only for the simplest model--three taxa, two state characters, under a molecular clock. Four taxa rooted trees have two topologies--the fork (two subtrees with two leaves each) and the comb (one subtree with three leaves, the other with a single leaf). In a previous work, we devised a closed form analytic solution for the ML molecular clock fork. In this work, we extend the state of the art in the area of analytic solutions ML trees to the family of all four taxa trees under the molecular clock assumption. The change from the fork topology to the comb incurs a major increase in the complexity of the underlying algebraic system and requires novel techniques and approaches. We combine the ultrametric properties of molecular clock trees with the Hadamard conjugation to derive a number of topology dependent identities. Employing these identities, we substantially simplify the system of polynomial equations. We finally use tools from algebraic geometry (e.g., Gröbner bases, ideal saturation, resultants) and employ symbolic algebra software to obtain analytic solutions for the comb. We show that in contrast to the fork, the comb has no closed form solutions (expressed by radicals in the input data). In general, four taxa trees can have multiple ML points. In contrast, we can now prove that under the molecular clock assumption, the comb has a unique (local and global) ML point. (Such uniqueness was previously shown for the fork.).
Seymour, Roger S
2010-09-01
Effect of size of inflorescences, flowers and cones on maximum rate of heat production is analysed allometrically in 23 species of thermogenic plants having diverse structures and ranging between 1.8 and 600 g. Total respiration rate (, micromol s(-1)) varies with spadix mass (M, g) according to in 15 species of Araceae. Thermal conductance (C, mW degrees C(-1)) for spadices scales according to C = 18.5M(0.73). Mass does not significantly affect the difference between floral and air temperature. Aroids with exposed appendices with high surface area have high thermal conductance, consistent with the need to vaporize attractive scents. True flowers have significantly lower heat production and thermal conductance, because closed petals retain heat that benefits resident insects. The florets on aroid spadices, either within a floral chamber or spathe, have intermediate thermal conductance, consistent with mixed roles. Mass-specific rates of respiration are variable between species, but reach 900 nmol s(-1) g(-1) in aroid male florets, exceeding rates of all other plants and even most animals. Maximum mass-specific respiration appears to be limited by oxygen delivery through individual cells. Reducing mass-specific respiration may be one selective influence on the evolution of large size of thermogenic flowers.
1997-01-01
Gateway Technologies, Inc. is marketing and developing textile insulation technology originally developed by Triangle Research and Development Corporation. The enhanced thermal insulation stems from Small Business Innovation Research contracts from NASA's Johnson Space Center and the U.S. Air Force. The effectiveness of the insulation comes from the microencapsulated phase-change materials originally made to keep astronauts gloved hands warm. The applications for the product range from outer wear, housing insulation, and blankets to protective firefighting gear and scuba diving suits. Gateway has developed and begun marketing thermal regulating products under the trademark, OUTLAST. Products made from OUTLAST are already on the market, including boot and shoe liners, winter headgear, hats and caps for hunting and other outdoor sports, and a variety of men's and women's ski gloves.
A mid-Holocene thermal maximum at the end of the African Humid Period
Berke, M.A.; Johnson, T.C.; Werne, J.P.; Schouten, S.; Sinninghe Damsté, J.S.
2012-01-01
The termination of the African Humid Period (AHP) about 5 thousand years ago (ka) was the most dramatic climate shift in northern and equatorial Africa since the end of the Pleistocene. Based on TEX86 paleotemperature data from lake Turkana, Kenya, we show that a temperature shift of 2-4 degrees C o
Dinocyst taphonomy, impact craters, cyst ghosts, and the Paleocene-Eocene thermal maximum (PETM)
Edwards, Lucy E.
2012-01-01
Dinocysts recovered from sediments related to the Chesapeake Bay impact structure in Virginia and the earliest Eocene suboxic environment in Maryland show strange and intriguing details of preservation. Features such as curled processes, opaque debris, breakage, microborings and cyst ghosts, among others, invite speculation about catastrophic depositional processes, rapid burial and biological and chemical decay. Selected specimens from seven cores taken in the coastal plain of Virginia and Maryland show abnormal preservation features in various combinations that merit illustration, description, discussion and further study. Although the depositional environments described are extreme, many of the features discussed are known from, or could be found in, other environments. These environments will show both similarities to and differences from the extreme environments here.
A mid-Holocene thermal maximum at the end of the African Humid Period
Berke, M.A.; Johnson, T.C.; Werne, J.P.; Schouten, S.; Sinninghe Damsté, J.S.
2012-01-01
The termination of the African Humid Period (AHP) about 5 thousand years ago (ka) was the most dramatic climate shift in northern and equatorial Africa since the end of the Pleistocene. Based on TEX86 paleotemperature data from lake Turkana, Kenya, we show that a temperature shift of 2-4 degrees C
Fucugauchi, J. U.; Perez-Cruz, L. L.
2015-12-01
Chicxulub formed 66 Ma ago by an asteroid impact on the Yucatan carbonate platform, southern Gulf of Mexico. Impact produced a 200 km diameter crater, platform fracturing, deformation and ejecta emplacement. Carbonate sedimentation restarted and crater was covered by up to 1 km of sediments. Drilling programs have sampled the Paleogene sediments, which record the changing sedimentation processes in the impact basin and platform. Here, results of a study of the Paleocene-Eocene sediments cored in the Santa Elena borehole are used to characterize the K/Pg and PETM. The borehole reached a depth of 504 m and was continuously cored, sampling the post-impact sediments and impact breccias, with contact at 332 m. For this study, we analyzed the section from ~230 to ~340 m, corresponding to the upper breccias and Paleocene-Eocene sediments. The lithological column, constructed from macroscopic and thin-section petrographic analyses, is composed of limestones and dolomitized limestones with several thin clay layers. Breccias are melt and basement clast rich, described as a suevitic unit. Section is further investigated using paleomagnetic, rock magnetic, X-ray fluorescence geochemical and stable isotope analyses. Magnetic polarities define a sequence of reverse to normal, which correlate to the geomagnetic polarity time scale from chrons 29r to 26r. The d13 C values in the first 20 m interval range from 1.2 to 3.5 %0 and d18 O values range from -1.4 to -4.8 %0. Isotope values show variation trends that correlate with the marine carbon and oxygen isotope patterns for the K-Pg boundary and early Paleocene. Positive carbon isotopes suggest relatively high productivity, with apparent recovery following the K-Pg extinction event. Geochemical data define characteristic trends, with Si decreasing gradually from high values in the suevites, low contents in Paleocene sediments with intervals of higher variability and then increased values likely marking the PETM. Variation trends are similar in other elements like Fe, Ti, K and Al, recording changing conditions in the platform. Ca shows the opposite trend, with low values in the suevites, higher values in Paleocene carbonates and lower values at PETM. Variations are interpreted in terms of the impact, hydrothermal activity, platform carbonate deposition and the PETM.
Climate, carbon cycling and marine ecology during the Paleocene-Eocene Thermal Maximum
Frieling, J.
2016-01-01
The Paleocene and Eocene are characterized by strong greenhouse climates. Atmospheric CO2 concentrations and global temperatures were much higher than today. The period from 60 to 50 million years ago (Ma) is marked by a gradual warming trend of ~8 ºC in the deep ocean. The interval from 56 to 50 Ma
Dunkley Jones, T.; Lunt, D.J.; Schmidt, D.N.; Ridgwell, A.; Sluijs, A.; Valdes, P.J.; Maslin, M.
2013-01-01
Constraining the greenhouse gas forcing, climatic warming and estimates of climate sensitivity across ancient large transient warming events is a major challenge to the palaeoclimate research community. Here we provide a new compilation and synthesis of the available marine proxy temperature data ac
Clague, John J.; Mathewes, R. W.
1989-03-01
Conifer logs and branches of early Holocene age are common on the surface and in sediments above timberline at Castle Peak in the southeastern Coast Mountains of British Columbia. A study of this wood and associated peat and colluvium has shown that local timberline from 9.1 to 8.2 ka was at least 60 m, and perhaps more than 130 m, higher than today. Mean growing-season temperature at Castle Peak during this period thus may have been 0.4-0.8°C warmer than at present. This is consistent with theoretical considerations based on Milankovitch forcing of climatic change and is supported by other paleoecological data from the southern Canadian Cordillera and adjacent northwestern United States. A generally warm climate may have persisted until about 5-6 ka, followed by late Holocene cooling.
Climate, carbon cycling and marine ecology during the Paleocene-Eocene Thermal Maximum
Frieling, J.
2016-01-01
The Paleocene and Eocene are characterized by strong greenhouse climates. Atmospheric CO2 concentrations and global temperatures were much higher than today. The period from 60 to 50 million years ago (Ma) is marked by a gradual warming trend of ~8 ºC in the deep ocean. The interval from 56 to 50 Ma
Fire and ecosystem change in the Arctic across the Paleocene-Eocene Thermal Maximum
Denis, E.H.; Pedentchouk, N.; Schouten, S.; Pagani, M.; Freeman, K.H.
2017-01-01
Fire has been an important component of ecosystems on a range of spatial and temporal scales. Fire can affect vegetation distribution, the carbon cycle, and climate. The relationship between climate and fire is complex, in large part because of a key role of vegetation type. Here, we evaluate
The response of the southern Greenland ice sheet to the Holocene thermal maximum
Larsen, Nicolaj Krog; Kjaer, Kurt H.; Lecavalier, Benoit
2015-01-01
in Greenland were 2–4 °C warmer than the present. Records from five new threshold lakes complemented with existing geological data from south of 70°N show that the ice margin was retracted behind its present-day extent in all sectors for a limited period between ca. 7 and 4 cal. kyr B.P. and in most sectors...
Evaluation of properties and thermal stress field for thermal barrier coatings
王良; 齐红宇; 杨晓光; 李旭
2008-01-01
In order to get thermal stress field of the hot section with thermal barrier coating (TBCs), the thermal conductivity and elastic modulus of top-coat are the physical key properties. The porosity of top-coat was tested and evaluated under different high temperatures. The relationship between the microstructure (porosity of top-coat) and properties of TBCs were analyzed to predict the thermal properties of ceramic top-coat, such as thermal conductivity and elastic modulus. The temperature and stress field of the vane with TBCs were simulated using two sets of thermal conductivity data and elastic modulus, which are from literatures and this work, respectively. The results show that the temperature and stress distributions change with thermal conductivity and elastic modulus. The differences of maximum temperatures and stress are 6.5% and 8.0%, respectively.
Heat transfer and thermal stress analysis in grooved tubes
Veysel Özceyhan; Necdet Altuntop
2005-08-01
Heat transfer and thermal stresses, induced by temperature differencesin the internally grooved tubes of heat transfer equipment, have been analysed numerically. The analysis has been conducted for four different kinds of internally grooved tubes and three different mean inlet water velocities. Constant temperature was applied from the external surface of the tube. Energy and governing ﬂow equations were solved using ﬁnite difference scheme. Finite element method (FEM) was used to compute the thermal stress ﬁelds. Grooving effects on the thermal stress ratio have been discussed. As a result, maximum thermal stress occurs in the case of $p = d$ for all water inlet velocities. The maximum thermal stress ratio positions inside the tube have been indicated as MX for all investigated cases. In the light of the thermal stress values, various designs can be applied to reduce thermal stress in grooved tubes.
The Prediction of Maximum Amplitudes of Solar Cycles and the Maximum Amplitude of Solar Cycle 24
无
2002-01-01
We present a brief review of predictions of solar cycle maximum ampli-tude with a lead time of 2 years or more. It is pointed out that a precise predictionof the maximum amplitude with such a lead-time is still an open question despiteprogress made since the 1960s. A method of prediction using statistical character-istics of solar cycles is developed: the solar cycles are divided into two groups, ahigh rising velocity (HRV) group and a low rising velocity (LRV) group, dependingon the rising velocity in the ascending phase for a given duration of the ascendingphase. The amplitude of Solar Cycle 24 can be predicted after the start of thecycle using the formula derived in this paper. Now, about 5 years before the startof the cycle, we can make a preliminary prediction of 83.2-119.4 for its maximumamplitude.
Pattern formation, logistics, and maximum path probability
Kirkaldy, J. S.
1985-05-01
The concept of pattern formation, which to current researchers is a synonym for self-organization, carries the connotation of deductive logic together with the process of spontaneous inference. Defining a pattern as an equivalence relation on a set of thermodynamic objects, we establish that a large class of irreversible pattern-forming systems, evolving along idealized quasisteady paths, approaches the stable steady state as a mapping upon the formal deductive imperatives of a propositional function calculus. In the preamble the classical reversible thermodynamics of composite systems is analyzed as an externally manipulated system of space partitioning and classification based on ideal enclosures and diaphragms. The diaphragms have discrete classification capabilities which are designated in relation to conserved quantities by descriptors such as impervious, diathermal, and adiabatic. Differentiability in the continuum thermodynamic calculus is invoked as equivalent to analyticity and consistency in the underlying class or sentential calculus. The seat of inference, however, rests with the thermodynamicist. In the transition to an irreversible pattern-forming system the defined nature of the composite reservoirs remains, but a given diaphragm is replaced by a pattern-forming system which by its nature is a spontaneously evolving volume partitioner and classifier of invariants. The seat of volition or inference for the classification system is thus transferred from the experimenter or theoretician to the diaphragm, and with it the full deductive facility. The equivalence relations or partitions associated with the emerging patterns may thus be associated with theorems of the natural pattern-forming calculus. The entropy function, together with its derivatives, is the vehicle which relates the logistics of reservoirs and diaphragms to the analog logistics of the continuum. Maximum path probability or second-order differentiability of the entropy in isolation are
Yamamoto, R.; Asada, Y.; Matsuo, Y.; Mikoda, M.
1985-07-16
A thermal insulator comprises an expanded resin body having embedded therein an evacuated powder insulation portion which consists of fine powder and a container of film-like plastics or a film-like composite of plastics and metal for enclosing the powder. The resin body has been expanded by a Freon gas as a blowing agent. Since a Freon gas has a larger molecular diameter than the constituent gases of air, it is less likely to permeate through the container than air. Thus present invention provides a novel composite insulator which fully utilizes the benefits of vacuum insulation without necessitating a strong and costly material for a vacuum container.
赵柳
2011-01-01
The group G of general coordinate transformations on the thermodynamic configuration space ε spanned by all the extensive variables keeps the first law of thermodynamics invariant. One can introduce a metric with Lorentzian signature on the space ε, with the corresponding line element also being invariant under the action of G. This line element is identi6ed as the square of the proper entropy. Thus the second law of thermodynamics is also formulated invariantly and this lays down the foundation for the principle of thermal relativity.
Cardiorespiratory Fitness of Inmates of a Maximum Security Prison ...
USER
Maximum Security Prison; and also to determine the effects of age, gender, and period of incarceration on CRF. A total of 247 apparently healthy inmates of Maiduguri Maximum Security ... with different types of cardiovascular and metabolic.
Maximum likelihood polynomial regression for robust speech recognition
LU Yong; WU Zhenyang
2011-01-01
The linear hypothesis is the main disadvantage of maximum likelihood linear re- gression （MLLR）. This paper applies the polynomial regression method to model adaptation and establishes a nonlinear model adaptation algorithm using maximum likelihood polyno
Maximum flux density of the gyrosynchrotron spectrum in a nonuniform source
Ai-Hua Zhou; Rong-Chuan Wang; Cheng-Wen Shao
2009-01-01
The maximum flux density of a gyrosynchrotron radiation spectrum in a mag- netic dip|oe model with self absorption and gyroresonance is calculated. Our calculations show that the maximum flux density of the gyrosynchrotron spectrum increases with in- creasing low-energy cutoff, number density, input depth of energetic electrons, magnetic field strength and viewing angle, and with decreasing energy spectral index of energetic electrons, number density and temperature of thermal electrons. It is found that there are linear correlations between the logarithms of the maximum flux density and the above eight parameters with correlation coefficients higher than 0.91 and fit accuracies better than 10%. The maximum flux density could be a good indicator of the changes of these source parameters. In addition, we find that there are very good positive linear correla- tions between the logarithms of the maximum flux density and peak frequency when the above former five parameters vary respectively. Their linear correlation coefficients are higher than 0.90 and the fit accuracies are better than 0.5%.
A thermoelectric generator using loop heat pipe and design match for maximum-power generation
Huang, Bin-Juine
2015-09-05
The present study focuses on the thermoelectric generator (TEG) using loop heat pipe (LHP) and design match for maximum-power generation. The TEG uses loop heat pipe, a passive cooling device, to dissipate heat without consuming power and free of noise. The experiments for a TEG with 4W rated power show that the LHP performs very well with overall thermal resistance 0.35 K W-1, from the cold side of TEG module to the ambient. The LHP is able to dissipate heat up to 110W and is maintenance free. The TEG design match for maximum-power generation, called “near maximum-power point operation (nMPPO)”, is studied to eliminate the MPPT (maximum-power point tracking controller). nMPPO is simply a system design which properly matches the output voltage of TEG with the battery. It is experimentally shown that TEG using design match for maximum-power generation (nMPPO) performs better than TEG with MPPT.
M. Mihelich
2014-11-01
Full Text Available We derive rigorous results on the link between the principle of maximum entropy production and the principle of maximum Kolmogorov–Sinai entropy using a Markov model of the passive scalar diffusion called the Zero Range Process. We show analytically that both the entropy production and the Kolmogorov–Sinai entropy seen as functions of f admit a unique maximum denoted fmaxEP and fmaxKS. The behavior of these two maxima is explored as a function of the system disequilibrium and the system resolution N. The main result of this article is that fmaxEP and fmaxKS have the same Taylor expansion at first order in the deviation of equilibrium. We find that fmaxEP hardly depends on N whereas fmaxKS depends strongly on N. In particular, for a fixed difference of potential between the reservoirs, fmaxEP(N tends towards a non-zero value, while fmaxKS(N tends to 0 when N goes to infinity. For values of N typical of that adopted by Paltridge and climatologists (N ≈ 10 ~ 100, we show that fmaxEP and fmaxKS coincide even far from equilibrium. Finally, we show that one can find an optimal resolution N* such that fmaxEP and fmaxKS coincide, at least up to a second order parameter proportional to the non-equilibrium fluxes imposed to the boundaries. We find that the optimal resolution N* depends on the non equilibrium fluxes, so that deeper convection should be represented on finer grids. This result points to the inadequacy of using a single grid for representing convection in climate and weather models. Moreover, the application of this principle to passive scalar transport parametrization is therefore expected to provide both the value of the optimal flux, and of the optimal number of degrees of freedom (resolution to describe the system.
Thermal analysis of underground power cable system
Rerak, Monika; Ocłoń, Paweł
2017-10-01
The paper presents the application of Finite Element Method in thermal analysis of underground power cable system. The computations were performed for power cables buried in-line in the ground at a depth of 2 meters. The developed mathematical model allows determining the two-dimensional temperature distribution in the soil, thermal backfill and power cables. The simulations studied the effect of soil and cable backfill thermal conductivity on the maximum temperature of the cable conductor. Also, the effect of cable diameter on the temperature of cable core was studied. Numerical analyses were performed based on a program written in MATLAB.
20 CFR 617.14 - Maximum amount of TRA.
2010-04-01
... 20 Employees' Benefits 3 2010-04-01 2010-04-01 false Maximum amount of TRA. 617.14 Section 617.14... FOR WORKERS UNDER THE TRADE ACT OF 1974 Trade Readjustment Allowances (TRA) § 617.14 Maximum amount of TRA. (a) General rule. Except as provided under paragraph (b) of this section, the maximum amount of...
40 CFR 94.107 - Determination of maximum test speed.
2010-07-01
... specified in 40 CFR 1065.510. These data points form the lug curve. It is not necessary to generate the... 40 Protection of Environment 20 2010-07-01 2010-07-01 false Determination of maximum test speed... Determination of maximum test speed. (a) Overview. This section specifies how to determine maximum test...
14 CFR 25.1505 - Maximum operating limit speed.
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Maximum operating limit speed. 25.1505... Operating Limitations § 25.1505 Maximum operating limit speed. The maximum operating limit speed (V MO/M MO airspeed or Mach Number, whichever is critical at a particular altitude) is a speed that may not...
Maximum Performance Tests in Children with Developmental Spastic Dysarthria.
Wit, J.; And Others
1993-01-01
Three Maximum Performance Tasks (Maximum Sound Prolongation, Fundamental Frequency Range, and Maximum Repetition Rate) were administered to 11 children (ages 6-11) with spastic dysarthria resulting from cerebral palsy and 11 controls. Despite intrasubject and intersubject variability in normal and pathological speakers, the tasks were found to be…
Maximum physical capacity testing in cancer patients undergoing chemotherapy
Knutsen, L.; Quist, M; Midtgaard, J
2006-01-01
BACKGROUND: Over the past few years there has been a growing interest in the field of physical exercise in rehabilitation of cancer patients, leading to requirements for objective maximum physical capacity measurement (maximum oxygen uptake (VO(2max)) and one-repetition maximum (1RM)) to determine...
Thermoelectric Power Generator Design for Maximum Power: It's All About ZT
McCarty, R.
2013-07-01
There is a significant amount of literature that discusses thermoelectric power generator (TEG) design, but much of it overly simplifies the design space and therefore the results have limited use in designing real-life systems. This paper develops a more comprehensive model of the thermal and electrical interactions of a TEG in a system with known hot-side and cold-side thermal resistances and corresponding constant system temperature differential. Two design scenarios are investigated for common TEG system applications. In one method, the power from a TEG is maximized for a given electrical load, simulating a case where the TEG is electrically in series with a known load such as a fan. In the second design scenario, the power from a TEG is maximized for a given electrical load resistance ratio, n (the ratio between the external load resistance and the internal TEG resistance), simulating an application where the TEG is electrically in series with a load-matching converter. An interesting conclusion from this work is that, in the first design scenario, the electrical load resistance ratio, n, that maximizes TEG power occurs at √{1 + ZT} (where ZT is the thermoelectric figure of merit) instead of 1 as reported previously in literature. Equally interesting is that, if you define an analogous thermal resistance ratio, m' (representing the ratio between the TEG thermal resistance at open-circuit conditions and the system thermal resistance), the maximum power in both design scenarios occurs at √{1 + ZT} instead of the commonly cited value of 1. Furthermore, results are presented for real-life designs that incorporate electrical and thermal losses common to realistic TEG systems such as electrical contact resistance and thermal bypass around the TEG due to sealing.
Advanced Treatment Planning in Cancer Thermal Therapies
Theodoros SAMARAS; Esra NEUFELD; Niels KUSTER
2016-01-01
CEM43 thermal dose is a very common concept in thermal oncology. Thermal dose is the maximum amount of energy that can be transmitted during hyperthermia therapy conducted on temperature-sensitive tissue. Thermal dose is also the maximum value of local energy accumulation in human bodies, which can lead to tissue injury and pain. Thermal dose can also decrease the ifnishing temperature and reduce the energy to the tolerable range. There are two functions of the individualized hyperthermia treatment plan: it determines the setting and location that can realize the best tumor hyperthermia therapy; at the same time, it can decrease the effect of hyperthermia therapy on healthy tissues. There are four steps in the treatment plan of hyperthermia therapy for tumors: the ifrst step is to establish a three dimensional human body model and its corresponding an atomical structure that can be used in numerical algorithmvia medical imaging resources; the second step is to determine the volume of the electromagnetic energy accumulation. Based on the peculiarity of frequency and materials, even full-wave electromagnetic wave or quasi-static technique can be used to determine the tissue distribution. Evaluation of the therapy can be conducted based on thermal dose and the corresponding tissue damage model; the third step is to use Arrhenius model to provide direct evaluation of tissues in the thermal ablation zone, solidiifcation zone, as well as the necrotic area; the last step is the optimization of the treatment plan.
Westhoff, M.; Erpicum, S.; Archambeau, P.; Pirotton, M.; Zehe, E.; Dewals, B.
2015-12-01
Power can be performed by a system driven by a potential difference. From a given potential difference, the power that can be subtracted is constraint by the Carnot limit, which follows from the first and second laws of thermodynamics. If the system is such that the flux producing power (with power being the flux times its driving potential difference) also influences the potential difference, a maximum in power can be obtained as a result of the trade-off between the flux and the potential difference. This is referred to as the maximum power principle. It has already been shown that the atmosphere operates close to this maximum power limit when it comes to heat transport from the Equator to the poles, or vertically, from the surface to the atmospheric boundary layer. To reach this state of maximum power, the effective thermal conductivity of the atmosphere is adapted by the creation of convection cells. The aim of this study is to test if the soil's effective hydraulic conductivity also adapts in such a way that it produces maximum power. However, the soil's hydraulic conductivity adapts differently; for example by the creation of preferential flow paths. Here, this process is simulated in a lab experiment, which focuses on preferential flow paths created by piping. In the lab, we created a hydrological analogue to the atmospheric model dealing with heat transport between Equator and poles, with the aim to test if the effective hydraulic conductivity of the sand bed can be predicted with the maximum power principle. The experimental setup consists of two freely draining reservoir connected with each other by a confined aquifer. By adding water to only one reservoir, a potential difference will build up until a steady state is reached. The results will indicate whether the maximum power principle does apply for groundwater flow and how it should be applied. Because of the different way of adaptation of flow conductivity, the results differ from that of the
A thermal study of an encapsulated electrical transformer
Garcia, A. [Unidad Geotermia, Temixco (Mexico). Instituto de Investigaciones Electricas; Espinosa-Paredes, G. [Universidad Autonoma Metropolitana, Vicentina (Mexico). Dpto. de Ingenieria de Procesos e Hidraulica; Hernandez, I. [Centro de Sistemas de Manufactura, Nuevo Leon (Mexico). Instituto Tecnologico y de Estudios Superiores de Monterrey
2002-11-01
A thermal study of a 45 KVA-prototype encapsulated transformer is described. Casting resin systems were used as insulating systems for encapsulated electric transformers. Normal transformer operation is at full load and, thus the conductor and insulating system becomes hot owing to current circulation through the winding. To determine the various temperature distributions throughout the transformer, the thermal properties of the insulating system and boundary conditions must be known, so that hot spots are located via numerical modelling and maximum permissible temperatures are not attained. Results presented herein include thermal conductivity, thermal diffusivity, and specific heat capacity. Thermal conductivity was obtained experimentally by means of the line-source technique at various temperatures, between room temperature and 155{sup o}C which is the thermal limit of class F insulators. The thermal diffusivity was obtained by parameter estimation by fitting an approximate analytical model to the temperature-time data of the thermal conductivity experiment. Specific heat capacity was obtained from the definition of thermal diffusivity and the insulating-system density. In order to improve the electrical performance of the transformer criteria, a numerical simulation of the different dielectric structures was made using computer program. The boundary conditions for the thermal simulation stage were also determined experimentally from temperature test runs. Finally, in order to obtain data for thermal design, a numerical simulation of the high tension winding was carried out. The thermal simulation stage was performed at different current densities in the conductor with and without electrostatic shields to determine the temperature field and maximum attainable temperatures. Maximum transformer temperature were found to be 15-20{sup o}C below its thermal limit and a correlation of maximum temperature as function of circulating current was developed for design
Araudo, Anabella T; Crilly, Aidan; Blundell, Katherine M
2016-01-01
It has been suggested that relativistic shocks in extragalactic sources may accelerate the highest energy cosmic rays. The maximum energy to which cosmic rays can be accelerated depends on the structure of magnetic turbulence near the shock but recent theoretical advances indicate that relativistic shocks are probably unable to accelerate particles to energies much larger than a PeV. We study the hotspots of powerful radiogalaxies, where electrons accelerated at the termination shock emit synchrotron radiation. The turnover of the synchrotron spectrum is typically observed between infrared and optical frequencies, indicating that the maximum energy of non-thermal electrons accelerated at the shock is < TeV for a canonical magnetic field of ~100 micro Gauss. Based on theoretical considerations we show that this maximum energy cannot be constrained by synchrotron losses as usually assumed, unless the jet density is unreasonably large and most of the jet upstream energy goes to non-thermal particles. We test ...
Berry, Vincent; Nicolas, François
2006-01-01
Given a set of evolutionary trees on a same set of taxa, the maximum agreement subtree problem (MAST), respectively, maximum compatible tree problem (MCT), consists of finding a largest subset of taxa such that all input trees restricted to these taxa are isomorphic, respectively compatible. These problems have several applications in phylogenetics such as the computation of a consensus of phylogenies obtained from different data sets, the identification of species subjected to horizontal gene transfers and, more recently, the inference of supertrees, e.g., Trees Of Life. We provide two linear time algorithms to check the isomorphism, respectively, compatibility, of a set of trees or otherwise identify a conflict between the trees with respect to the relative location of a small subset of taxa. Then, we use these algorithms as subroutines to solve MAST and MCT on rooted or unrooted trees of unbounded degree. More precisely, we give exact fixed-parameter tractable algorithms, whose running time is uniformly polynomial when the number of taxa on which the trees disagree is bounded. The improves on a known result for MAST and proves fixed-parameter tractability for MCT.
Thermal Implications for Extreme Fast Charge
Keyser, Matthew A [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-08-14
Present-day thermal management systems for battery electric vehicles are inadequate in limiting the maximum temperature rise of the battery during extreme fast charging. If the battery thermal management system is not designed correctly, the temperature of the cells could reach abuse temperatures and potentially send the cells into thermal runaway. Furthermore, the cell and battery interconnect design needs to be improved to meet the lifetime expectations of the consumer. Each of these aspects is explored and addressed as well as outlining where the heat is generated in a cell, the efficiencies of power and energy cells, and what type of battery thermal management solutions are available in today's market. Thermal management is not a limiting condition with regard to extreme fast charging, but many factors need to be addressed especially for future high specific energy density cells to meet U.S. Department of Energy cost and volume goals.
Theoretical Evaluation of the Maximum Work of Free-Piston Engine Generators
Kojima, Shinji
2017-01-01
Utilizing the adjoint equations that originate from the calculus of variations, we have calculated the maximum thermal efficiency that is theoretically attainable by free-piston engine generators considering the work loss due to friction and Joule heat. Based on the adjoint equations with seven dimensionless parameters, the trajectory of the piston, the histories of the electric current, the work done, and the two kinds of losses have been derived in analytic forms. Using these we have conducted parametric studies for the optimized Otto and Brayton cycles. The smallness of the pressure ratio of the Brayton cycle makes the net work done negative even when the duration of heat addition is optimized to give the maximum amount of heat addition. For the Otto cycle, the net work done is positive, and both types of losses relative to the gross work done become smaller with the larger compression ratio. Another remarkable feature of the optimized Brayton cycle is that the piston trajectory of the heat addition/disposal process is expressed by the same equation as that of an adiabatic process. The maximum thermal efficiency of any combination of isochoric and isobaric heat addition/disposal processes, such as the Sabathe cycle, may be deduced by applying the methods described here.
Maximum cycle work output optimization for generalized radiative law Otto cycle engines
Xia, Shaojun; Chen, Lingen; Sun, Fengrui
2016-11-01
An Otto cycle internal combustion engine which includes thermal and friction losses is investigated by finite-time thermodynamics, and the optimization objective is the maximum cycle work output. The thermal energy transfer from the working substance to the cylinder inner wall follows the generalized radiative law (q∝Δ (Tn)). Under the condition that all of the fuel consumption, the compression ratio and the cycle period are given, the optimal piston trajectories for both the examples with unlimited and limited accelerations on every stroke are determined, and the cycle-period distribution among all strokes is also optimized. Numerical calculation results for the case of radiative law are provided and compared with those obtained for the cases of Newtonian law and linear phenomenological law. The results indicate that the optimal piston trajectory on each stroke contains three sections, which consist of an original maximum-acceleration and a terminal maximum-deceleration parts; for the case of radiative law, optimizing the piston motion path can achieve an improvement of more than 20% in both the cycle-work output and the second-law efficiency of the Otto cycle compared with the conventional near-sinusoidal operation, and heat transfer mechanisms have both qualitative and quantitative influences on the optimal paths of piston movements.
Thermal analysis of the SSC beam scraper
Tran, N.; Dao, B.
1993-04-01
When a particle beam impacts a beam scraper, heat is generated resulting in a rise in the temperature of the material. The maximum temperature rise should be kept to a minimum in order to maintain scraper efficiency and performance. In this paper the results of a thermal analysis of a scraper are presented.
A Thermal Oscillating Two-Stream Instability
Dysthe, K. B.; Mjølhus, E.; Pécseli, H. L.
1983-01-01
, and transverse scale of maximum growth are obtained. Special attention is paid to the transport theory, since the physical picture depends heavily on the kind of electron collisions which dominate. This is due to the velocity dependence of collison frequencies, which gives rise to the thermal forces....
Thermal conductivity of thermal-battery insulations
Guidotti, R.A.; Moss, M.
1995-08-01
The thermal conductivities of a variety of insulating materials used in thermal batteries were measured in atmospheres of argon and helium using several techniques. (Helium was used to simulate the hydrogen atmosphere that results when a Li(Si)/FeS{sub 2} thermal battery ages.) The guarded-hot-plate method was used with the Min-K insulation because of its extremely low thermal conductivity. For comparison purposes, the thermal conductivity of the Min-K insulating board was also measured using the hot-probe method. The thermal-comparator method was used for the rigid Fiberfrax board and Fiberfrax paper. The thermal conductivity of the paper was measured under several levels of compression to simulate the conditions of the insulating wrap used on the stack in a thermal battery. The results of preliminary thermal-characterization tests with several silica aerogel materials are also presented.
Santos W. N. dos
2003-01-01
Full Text Available The hot wire technique is considered to be an effective and accurate means of determining the thermal conductivity of ceramic materials. However, specifically for materials of high thermal diffusivity, the appropriate time interval to be considered in calculations is a decisive factor for getting accurate and consistent results. In this work, a numerical simulation model is proposed with the aim of determining the minimum and maximum measuring time for the hot wire parallel technique. The temperature profile generated by this model is in excellent agreement with that one experimentally obtained by this technique, where thermal conductivity, thermal diffusivity and specific heat are simultaneously determined from the same experimental temperature transient. Eighteen different specimens of refractory materials and polymers, with thermal diffusivities ranging from 1x10-7 to 70x10-7 m²/s, in shape of rectangular parallelepipeds, and with different dimensions were employed in the experimental programme. An empirical equation relating minimum and maximum measuring times and the thermal diffusivity of the sample is also obtained.
Thomas, Catherine [Paris-11 Univ., 91 Orsay (France)
2000-01-19
Theoretical models have shown that the maximum magnetic field in radio frequency superconducting cavities is the superheating field H{sub sh}. For niobium, H{sub sh} is 25 - 30% higher than the thermodynamical H{sub c} field: H{sub sh} within (240 - 274) mT. However, the maximum magnetic field observed so far is in the range H{sub c,max} = 152 mT for the best 1.3 GHz Nb cavities. This field is lower than the critical field H{sub c1} above which the superconductor breaks up into divided normal and superconducting zones (H{sub c1}{<=}H{sub c}). Thermal instabilities are responsible for this low value. In order to reach H{sub sh} before thermal breakdown, high power short pulses are used. The cavity needs then to be strongly over-coupled. The dedicated test bed has been built from the collaboration between Istituto Nazionale di Fisica Nucleare (INFN) - Sezione di Genoa, and the Service d'Etudes et Realisation d'Accelerateurs (SERA) of Laboratoire de l'Accelerateur Lineaire (LAL). The maximum magnetic field, H{sub rf,max}, measurements on INFN cavities give lower results than the theoretical speculations and are in agreement with previous results. The superheating magnetic fields is linked to the magnetic penetration depth. This superconducting characteristic length can be used to determine the quality of niobium through the ratio between the resistivity measured at 300 K and 4.2 K in the normal conducting state (RRR). Results have been compared to previous ones and agree pretty well. They show that the RRR measured on cavities is superficial and lower than the RRR measured on samples which concerns the volume. (author)
A review of passive thermal management of LED module
Ye, H.; Sau, K.; Zeijl, H. van; Gielen, A.W.J.; Zhang, G.
2011-01-01
Recently, the high-brightness LEDs have begun to be designed for illumination application. The increased electrical currents used to drive LEDs lead to thermal issues. Thermal management for LED module is a key design parameter as high operation temperature directly affects their maximum light outpu
Present and Last Glacial Maximum climates as states of maximum entropy production
Herbert, Corentin; Kageyama, Masa; Dubrulle, Berengere
2011-01-01
The Earth, like other planets with a relatively thick atmosphere, is not locally in radiative equilibrium and the transport of energy by the geophysical fluids (atmosphere and ocean) plays a fundamental role in determining its climate. Using simple energy-balance models, it was suggested a few decades ago that the meridional energy fluxes might follow a thermodynamic Maximum Entropy Production (MEP) principle. In the present study, we assess the MEP hypothesis in the framework of a minimal climate model based solely on a robust radiative scheme and the MEP principle, with no extra assumptions. Specifically, we show that by choosing an adequate radiative exchange formulation, the Net Exchange Formulation, a rigorous derivation of all the physical parameters can be performed. The MEP principle is also extended to surface energy fluxes, in addition to meridional energy fluxes. The climate model presented here is extremely fast, needs very little empirical data and does not rely on ad hoc parameterizations. We in...
Balusek, Alan R.
2009-01-01
A thermal test overview of the Constellation Environmental Qualification and Acceptance Test Requirement (CEQATR) is presented. The contents include: 1) CEQATR Thermal Test Overview; 2) CxP Environments; 3) CEQATR Table 1.2-1; 4) Levels of Assembly; 5) Definitions for Levels of Assembly; 6) Hardware Applicability; 7) CEQATR Thermal-Related Definitions; 8) Requirements for unit-level thermal testing; 9) Requirements for major assembly level thermal testing; 10) General thermal testing requirements; 11) General thermal cycle, thermal vacuum profiles; 12) Test tolerances; 13) Vacuum vs Ambient; 14) Thermal Gradient; 15) Sequence of Testing; 16) Alternative Strategies; 17) Protoflight; 18) Halt/Hass; 19) Humidity; and 20) Tailoring.
Simulation of Nuclear Thermal Radiation with High Intensity Flashlamps.
1979-01-26
lators. Thermal test requirements often stress only one aspect of nuclear radiation at a time, i.e., maximum flux, UV exposure, etc. Hardness tests...DoE/STTF* furnace at Sandia/Albuquerque is presently capable of low *Solar Thermal Test Facility, now renamed Central Receiver Test Facil- ity (CRTF...Viewpoint," a paper presented at the annual meeting of the Solar Thermal Test Facilities Users Association, Golden, Colorado, April 11-12, 1978. 2. T
A Note on k-Limited Maximum Base
Yang Ruishun; Yang Xiaowei
2006-01-01
The problem of k-limited maximum base was specified into two special problems of k-limited maximum base; that is, let subset D of the problem of k-limited maximum base be an independent set and a circuit of the matroid, respectively. It was proved that under this circumstance the collections of k-limited base satisfy base axioms. Then a new matroid was determined, and the problem of k-limited maximum base was transformed to the problem of maximum base of this new matroid. Aiming at the problem, two algorithms, which in essence are greedy algorithms based on former matroid, were presented for the two special problems of k-limited maximum base. They were proved to be reasonable and more efficient than the algorithm presented by Ma Zhongfan in view of the complexity of algorithm.
Vaudrey, A; Lanzetta, F; Glises, R
2009-01-01
Producing useful electrical work in consuming chemical energy, the fuel cell have to reject heat to its surrounding. However, as it occurs for any other type of engine, this thermal energy cannot be exchanged in an isothermal way in finite time through finite areas. As it was already done for various types of systems, we study the fuel cell within the finite time thermodynamics framework and define an endoreversible fuel cell. Considering different types of heat transfer laws, we obtain an optimal value of the operating temperature, corresponding to a maximum produced power. This analysis is a first step of a thermodynamical approach of design of thermal management devices, taking into account performances of the whole system.
Theoretical study of the seasonal behavior of the global ionosphere at solar maximum
Sojka, J. J.; Schunk, R. W.
1989-01-01
The seasonal behavior of the global ionosphere was studied using a time-dependent three-dimensional physical model (developed by Shunk and his coworkers) of the ionosphere at altitudes between 120 and 800 km. This model accounts for field-aligned diffusion, cross-field electrodynamic drifts both the equatorial region and at high latitudes, interhemispheric flow, thermospheric winds, polar wind escape, energy-dependent chemical reactions, neutral composition changes, ion production due to solar EUV radiation and auroral precipitation, thermal conduction, diffusion-thermal heat flow, and local heating and cooling processes. The model studies were carried out for both June and December solstice conditions at solar maximum and for low geomagnetic activity. The ionospheric features predicted by the model agreed qualitatively with the available measurements.
On the maximum-entropy method for kinetic equation of radiation, particle and gas
El-Wakil, S.A. [Mansoura Univ. (Egypt). Phys. Dept.; Madkour, M.A. [Mansoura Univ. (Egypt). Phys. Dept.; Degheidy, A.R. [Mansoura Univ. (Egypt). Phys. Dept.; Machali, H.M. [Mansoura Univ. (Egypt). Phys. Dept.
1995-02-01
The maximum-entropy approach is used to calculate some problems in radiative transfer and reactor physics such as the escape probability, the emergent and transmitted intensities for a finite slab as well as the emergent intensity for a semi-infinite medium. Also, it is employed to solve problems involving spherical geometry, such as luminosity (the total energy emitted by a sphere), neutron capture probability and the albedo problem. The technique is also employed in the kinetic theory of gases to calculate the Poiseuille flow and thermal creep of a rarefied gas between two plates. Numerical calculations are achieved and compared with the published data. The comparisons demonstrate that the maximum-entropy results are good in agreement with the exact ones. (orig.).
An Interval Maximum Entropy Method for Quadratic Programming Problem
RUI Wen-juan; CAO De-xin; SONG Xie-wu
2005-01-01
With the idea of maximum entropy function and penalty function methods, we transform the quadratic programming problem into an unconstrained differentiable optimization problem, discuss the interval extension of the maximum entropy function, provide the region deletion test rules and design an interval maximum entropy algorithm for quadratic programming problem. The convergence of the method is proved and numerical results are presented. Both theoretical and numerical results show that the method is reliable and efficient.
Hutchinson, Thomas H. [Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH (United Kingdom)], E-mail: thom1@pml.ac.uk; Boegi, Christian [BASF SE, Product Safety, GUP/PA, Z470, 67056 Ludwigshafen (Germany); Winter, Matthew J. [AstraZeneca Safety, Health and Environment, Brixham Environmental Laboratory, Devon TQ5 8BA (United Kingdom); Owens, J. Willie [The Procter and Gamble Company, Central Product Safety, 11810 East Miami River Road, Cincinnati, OH 45252 (United States)
2009-02-19
There is increasing recognition of the need to identify specific sublethal effects of chemicals, such as reproductive toxicity, and specific modes of actions of the chemicals, such as interference with the endocrine system. To achieve these aims requires criteria which provide a basis to interpret study findings so as to separate these specific toxicities and modes of action from not only acute lethality per se but also from severe inanition and malaise that non-specifically compromise reproductive capacity and the response of endocrine endpoints. Mammalian toxicologists have recognized that very high dose levels are sometimes required to elicit both specific adverse effects and present the potential of non-specific 'systemic toxicity'. Mammalian toxicologists have developed the concept of a maximum tolerated dose (MTD) beyond which a specific toxicity or action cannot be attributed to a test substance due to the compromised state of the organism. Ecotoxicologists are now confronted by a similar challenge and must develop an analogous concept of a MTD and the respective criteria. As examples of this conundrum, we note recent developments in efforts to validate protocols for fish reproductive toxicity and endocrine screens (e.g. some chemicals originally selected as 'negatives' elicited decreases in fecundity or changes in endpoints intended to be biomarkers for endocrine modes of action). Unless analogous criteria can be developed, the potentially confounding effects of systemic toxicity may then undermine the reliable assessment of specific reproductive effects or biomarkers such as vitellogenin or spiggin. The same issue confronts other areas of aquatic toxicology (e.g., genotoxicity) and the use of aquatic animals for preclinical assessments of drugs (e.g., use of zebrafish for drug safety assessment). We propose that there are benefits to adopting the concept of an MTD for toxicology and pharmacology studies using fish and other aquatic
Improved Reliability of Single-Phase PV Inverters by Limiting the Maximum Feed-in Power
Yang, Yongheng; Wang, Huai; Blaabjerg, Frede
2014-01-01
. The CPG control strategy is activated only when the DC input power from PV panels exceeds a specific power limit. It enables to limit the maximum feed-in power to the electric grids and also to improve the utilization of PV inverters. As a further study, this paper investigates the reliability performance...... of the power devices (e.g. IGBTs) used in PV inverters with the CPG control under different feed-in power limits. A long-term mission profile (i.e. solar irradiance and ambient temperature) based stress analysis approach is extended and applied to obtain the yearly electrical and thermal stresses of the power...
Abhijit Sinha
2014-01-01
Full Text Available A comparative analysis on thermodynamic efficiency based on maximum power & power density conditions have been performed for a solar-driven Carnot heat engine with internal irreversibility. In this analysis, the heat transfer from the hot reservoir is to be in the radiation mode and the heat transfer to the cold reservoir is to be in the convection mode. The thermodynamic efficiency function, power & power density functions have been derived and maximization of the power functions have been performed for various design parameters. From the optimum conditions, the thermal efficiencies at maximum power and power densities have been obtained. The effects of internal irreversibility, extreme temperature ratios & specific engine size in area ratio between the hot & cold reservoirs as various design parameters on thermodynamic efficiencies have been investigated for both the conditions. The efficiencies have been compared with Curzon-Ahlborn & Carnot efficiencies respectively.The analysis showed that the efficiency at maximum power output is greater than the efficiency at maximum power density. And the efficiencies can be greater than the Curzon- Ahlborn`s efficiency only for low values of design parameters.
Seasonal thermal energy storage
Allen, R.D.; Kannberg, L.D.; Raymond, J.R.
1984-05-01
This report describes the following: (1) the US Department of Energy Seasonal Thermal Energy Storage Program, (2) aquifer thermal energy storage technology, (3) alternative STES technology, (4) foreign studies in seasonal thermal energy storage, and (5) economic assessment.
CO2 maximum in the oxygen minimum zone (OMZ)
Paulmier, A.; Ruiz-Pino, D.; Garçon, V.
2011-02-01
Oxygen minimum zones (OMZs), known as suboxic layers which are mainly localized in the Eastern Boundary Upwelling Systems, have been expanding since the 20th "high CO2" century, probably due to global warming. OMZs are also known to significantly contribute to the oceanic production of N2O, a greenhouse gas (GHG) more efficient than CO2. However, the contribution of the OMZs on the oceanic sources and sinks budget of CO2, the main GHG, still remains to be established. We present here the dissolved inorganic carbon (DIC) structure, associated locally with the Chilean OMZ and globally with the main most intense OMZs (O22225 μmol kg-1, up to 2350 μmol kg-1) have been reported over the whole OMZ thickness, allowing the definition for all studied OMZs a Carbon Maximum Zone (CMZ). Locally off Chile, the shallow cores of the OMZ and CMZ are spatially and temporally collocated at 21° S, 30° S and 36° S despite different cross-shore, long-shore and seasonal configurations. Globally, the mean state of the main OMZs also corresponds to the largest carbon reserves of the ocean in subsurface waters. The CMZs-OMZs could then induce a positive feedback for the atmosphere during upwelling activity, as potential direct local sources of CO2. The CMZ paradoxically presents a slight "carbon deficit" in its core (~10%), meaning a DIC increase from the oxygenated ocean to the OMZ lower than the corresponding O2 decrease (assuming classical C/O molar ratios). This "carbon deficit" would be related to regional thermal mechanisms affecting faster O2 than DIC (due to the carbonate buffer effect) and occurring upstream in warm waters (e.g., in the Equatorial Divergence), where the CMZ-OMZ core originates. The "carbon deficit" in the CMZ core would be mainly compensated locally at the oxycline, by a "carbon excess" induced by a specific remineralization. Indeed, a possible co-existence of bacterial heterotrophic and autotrophic processes usually occurring at different depths could
CO2 maximum in the oxygen minimum zone (OMZ
V. Garçon
2011-02-01
Full Text Available Oxygen minimum zones (OMZs, known as suboxic layers which are mainly localized in the Eastern Boundary Upwelling Systems, have been expanding since the 20th "high CO2" century, probably due to global warming. OMZs are also known to significantly contribute to the oceanic production of N2O, a greenhouse gas (GHG more efficient than CO2. However, the contribution of the OMZs on the oceanic sources and sinks budget of CO2, the main GHG, still remains to be established. We present here the dissolved inorganic carbon (DIC structure, associated locally with the Chilean OMZ and globally with the main most intense OMZs (O2−1 in the open ocean. To achieve this, we examine simultaneous DIC and O2 data collected off Chile during 4 cruises (2000–2002 and a monthly monitoring (2000–2001 in one of the shallowest OMZs, along with international DIC and O2 databases and climatology for other OMZs. High DIC concentrations (>2225 μmol kg−1, up to 2350 μmol kg−1 have been reported over the whole OMZ thickness, allowing the definition for all studied OMZs a Carbon Maximum Zone (CMZ. Locally off Chile, the shallow cores of the OMZ and CMZ are spatially and temporally collocated at 21° S, 30° S and 36° S despite different cross-shore, long-shore and seasonal configurations. Globally, the mean state of the main OMZs also corresponds to the largest carbon reserves of the ocean in subsurface waters. The CMZs-OMZs could then induce a positive feedback for the atmosphere during upwelling activity, as potential direct local sources of CO2. The CMZ paradoxically presents a slight "carbon deficit" in its core (~10%, meaning a DIC increase from the oxygenated ocean to the OMZ lower than the corresponding O2 decrease (assuming classical C/O molar ratios. This "carbon deficit" would be related to regional thermal mechanisms affecting faster O2 than DIC (due to the carbonate buffer effect and occurring upstream in warm waters (e.g., in the Equatorial Divergence
THE MAXIMUM ENERGY OF ACCELERATED PARTICLES IN RELATIVISTIC COLLISIONLESS SHOCKS
Sironi, Lorenzo [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Spitkovsky, Anatoly [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544-1001 (United States); Arons, Jonathan, E-mail: lsironi@cfa.harvard.edu [Department of Astronomy, Department of Physics, and Theoretical Astrophysics Center, University of California, Berkeley, CA 94720 (United States)
2013-07-01
The afterglow emission from gamma-ray bursts (GRBs) is usually interpreted as synchrotron radiation from electrons accelerated at the GRB external shock that propagates with relativistic velocities into the magnetized interstellar medium. By means of multi-dimensional particle-in-cell simulations, we investigate the acceleration performance of weakly magnetized relativistic shocks, in the magnetization range 0 {approx}< {sigma} {approx}< 10{sup -1}. The pre-shock magnetic field is orthogonal to the flow, as generically expected for relativistic shocks. We find that relativistic perpendicular shocks propagating in electron-positron plasmas are efficient particle accelerators if the magnetization is {sigma} {approx}< 10{sup -3}. For electron-ion plasmas, the transition to efficient acceleration occurs for {sigma} {approx}< 3 Multiplication-Sign 10{sup -5}. Here, the acceleration process proceeds similarly for the two species, since the electrons enter the shock nearly in equipartition with the ions, as a result of strong pre-heating in the self-generated upstream turbulence. In both electron-positron and electron-ion shocks, we find that the maximum energy of the accelerated particles scales in time as {epsilon}{sub max}{proportional_to}t {sup 1/2}. This scaling is shallower than the so-called (and commonly assumed) Bohm limit {epsilon}{sub max}{proportional_to}t, and it naturally results from the small-scale nature of the Weibel turbulence generated in the shock layer. In magnetized plasmas, the energy of the accelerated particles increases until it reaches a saturation value {epsilon}{sub sat}/{gamma}{sub 0} m{sub i}c {sup 2} {approx} {sigma}{sup -1/4}, where {gamma}{sub 0} m{sub i}c {sup 2} is the mean energy per particle in the upstream bulk flow. Further energization is prevented by the fact that the self-generated turbulence is confined within a finite region of thickness {proportional_to}{sigma}{sup -1/2} around the shock. Our results can provide physically
Integer Programming Model for Maximum Clique in Graph
YUAN Xi-bo; YANG You; ZENG Xin-hai
2005-01-01
The maximum clique or maximum independent set of graph is a classical problem in graph theory. Combined with Boolean algebra and integer programming, two integer programming models for maximum clique problem,which improve the old results were designed in this paper. Then, the programming model for maximum independent set is a corollary of the main results. These two models can be easily applied to computer algorithm and software, and suitable for graphs of any scale. Finally the models are presented as Lingo algorithms, verified and compared by several examples.
Counterexamples to convergence theorem of maximum-entropy clustering algorithm
于剑; 石洪波; 黄厚宽; 孙喜晨; 程乾生
2003-01-01
In this paper, we surveyed the development of maximum-entropy clustering algorithm, pointed out that the maximum-entropy clustering algorithm is not new in essence, and constructed two examples to show that the iterative sequence given by the maximum-entropy clustering algorithm may not converge to a local minimum of its objective function, but a saddle point. Based on these results, our paper shows that the convergence theorem of maximum-entropy clustering algorithm put forward by Kenneth Rose et al. does not hold in general cases.
Solar Thermal Electricity Generating System
Mishra, Sambeet; Tripathy, Pratyasha
2012-08-01
A Solar Thermal Electricity generating system also known as Solar Thermal Power plant is an emerging renewable energy technology, where we generate the thermal energy by concentrating and converting the direct solar radiationat medium/high temperature (300∫C ñ 800∫C). The resulting thermal energy is then used in a thermodynamic cycleto produce electricity, by running a heat engine, which turns a generator to make electricity. Solar thermal power is currently paving the way for the most cost-effective solar technology on a large scale and is heading to establish a cleaner, pollution free and secured future. Photovoltaic (PV) and solar thermal technologies are two main ways of generating energy from the sun, which is considered the inexhaustible source of energy. PV converts sunlight directly into electricity whereas in Solar thermal technology, heat from the sun's rays is concentrated to heat a fluid, whose steam powers a generator that produces electricity. It is similar to the way fossil fuel-burning power plants work except that the steam is produced by the collected heat rather than from the combustion of fossil fuels. In order to generate electricity, five major varieties of solar thermal technologies used are:* Parabolic Trough Solar Electric Generating System (SEGS).* Central Receiver Power Plant.* Solar Chimney Power Plant.* Dish Sterling System.* Solar Pond Power Plant.Most parts of India,Asia experiences a clear sunny weather for about 250 to 300 days a year, because of its location in the equatorial sun belt of the earth, receiving fairly large amount of radiation as compared to many parts of the world especially Japan, Europe and the US where development and deployment of solar technologies is maximum.Whether accompanied with this benefit or not, usually we have to concentrate the solar radiation in order to compensate for the attenuation of solar radiation in its way to earthís surface, which results in from 63,2 GW/m2 at the Sun to 1 kW/m2 at
Combining Experiments and Simulations Using the Maximum Entropy Principle
Boomsma, Wouter; Ferkinghoff-Borg, Jesper; Lindorff-Larsen, Kresten
2014-01-01
are not in quantitative agreement with experimental data. The principle of maximum entropy is a general procedure for constructing probability distributions in the light of new data, making it a natural tool in cases when an initial model provides results that are at odds with experiments. The number of maximum entropy...
49 CFR 174.86 - Maximum allowable operating speed.
2010-10-01
... 49 Transportation 2 2010-10-01 2010-10-01 false Maximum allowable operating speed. 174.86 Section... operating speed. (a) For molten metals and molten glass shipped in packagings other than those prescribed in § 173.247 of this subchapter, the maximum allowable operating speed may not exceed 24 km/hour (15...
Parametric optimization of thermoelectric elements footprint for maximum power generation
Rezania, A.; Rosendahl, Lasse; Yin, Hao
2014-01-01
The development studies in thermoelectric generator (TEG) systems are mostly disconnected to parametric optimization of the module components. In this study, optimum footprint ratio of n- and p-type thermoelectric (TE) elements is explored to achieve maximum power generation, maximum cost-perform...
30 CFR 56.19066 - Maximum riders in a conveyance.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum riders in a conveyance. 56.19066 Section 56.19066 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Hoisting Hoisting Procedures § 56.19066 Maximum riders in a conveyance. In shafts inclined over 45...
30 CFR 57.19066 - Maximum riders in a conveyance.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum riders in a conveyance. 57.19066 Section 57.19066 Mineral Resources MINE SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR METAL AND... Hoisting Hoisting Procedures § 57.19066 Maximum riders in a conveyance. In shafts inclined over 45...
Maximum Atmospheric Entry Angle for Specified Retrofire Impulse
T. N. Srivastava
1969-07-01
Full Text Available Maximum atmospheric entry angles for vehicles initially moving in elliptic orbits are investigated and it is shown that tangential retrofire impulse at the apogee results in the maximum entry angle. Equivalence of maximizing the entry angle and minimizing the retrofire impulse is also established.
5 CFR 838.711 - Maximum former spouse survivor annuity.
2010-01-01
... 5 Administrative Personnel 2 2010-01-01 2010-01-01 false Maximum former spouse survivor annuity... Orders Awarding Former Spouse Survivor Annuities Limitations on Survivor Annuities § 838.711 Maximum former spouse survivor annuity. (a) Under CSRS, payments under a court order may not exceed the...
46 CFR 151.45-6 - Maximum amount of cargo.
2010-10-01
... 46 Shipping 5 2010-10-01 2010-10-01 false Maximum amount of cargo. 151.45-6 Section 151.45-6 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES BARGES CARRYING BULK LIQUID HAZARDOUS MATERIAL CARGOES Operations § 151.45-6 Maximum amount of cargo. (a)...
20 CFR 226.52 - Total annuity subject to maximum.
2010-04-01
... rate effective on the date the supplemental annuity begins, before any reduction for a private pension... 20 Employees' Benefits 1 2010-04-01 2010-04-01 false Total annuity subject to maximum. 226.52... COMPUTING EMPLOYEE, SPOUSE, AND DIVORCED SPOUSE ANNUITIES Railroad Retirement Family Maximum § 226.52...
49 CFR 195.406 - Maximum operating pressure.
2010-10-01
... 49 Transportation 3 2010-10-01 2010-10-01 false Maximum operating pressure. 195.406 Section 195... HAZARDOUS LIQUIDS BY PIPELINE Operation and Maintenance § 195.406 Maximum operating pressure. (a) Except for surge pressures and other variations from normal operations, no operator may operate a pipeline at a...
Maximum-entropy clustering algorithm and its global convergence analysis
无
2001-01-01
Constructing a batch of differentiable entropy functions touniformly approximate an objective function by means of the maximum-entropy principle, a new clustering algorithm, called maximum-entropy clustering algorithm, is proposed based on optimization theory. This algorithm is a soft generalization of the hard C-means algorithm and possesses global convergence. Its relations with other clustering algorithms are discussed.
Distribution of maximum loss of fractional Brownian motion with drift
Çağlar, Mine; Vardar-Acar, Ceren
2013-01-01
In this paper, we find bounds on the distribution of the maximum loss of fractional Brownian motion with H >= 1/2 and derive estimates on its tail probability. Asymptotically, the tail of the distribution of maximum loss over [0, t] behaves like the tail of the marginal distribution at time t.
48 CFR 436.575 - Maximum workweek-construction schedule.
2010-10-01
...-construction schedule. 436.575 Section 436.575 Federal Acquisition Regulations System DEPARTMENT OF AGRICULTURE... Maximum workweek-construction schedule. The contracting officer shall insert the clause at 452.236-75, Maximum Workweek-Construction Schedule, if the clause at FAR 52.236-15 is used and the contractor's...
30 CFR 57.5039 - Maximum permissible concentration.
2010-07-01
... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Maximum permissible concentration. 57.5039... Maximum permissible concentration. Except as provided by standard § 57.5005, persons shall not be exposed to air containing concentrations of radon daughters exceeding 1.0 WL in active workings. ...
5 CFR 550.105 - Biweekly maximum earnings limitation.
2010-01-01
... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Biweekly maximum earnings limitation. 550.105 Section 550.105 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY ADMINISTRATION (GENERAL) Premium Pay Maximum Earnings Limitations § 550.105 Biweekly...
5 CFR 550.106 - Annual maximum earnings limitation.
2010-01-01
... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Annual maximum earnings limitation. 550.106 Section 550.106 Administrative Personnel OFFICE OF PERSONNEL MANAGEMENT CIVIL SERVICE REGULATIONS PAY ADMINISTRATION (GENERAL) Premium Pay Maximum Earnings Limitations § 550.106 Annual...
32 CFR 842.35 - Depreciation and maximum allowances.
2010-07-01
... 32 National Defense 6 2010-07-01 2010-07-01 false Depreciation and maximum allowances. 842.35... LITIGATION ADMINISTRATIVE CLAIMS Personnel Claims (31 U.S.C. 3701, 3721) § 842.35 Depreciation and maximum allowances. The military services have jointly established the “Allowance List-Depreciation Guide”...
Zhang, Min-juan; Wang, Zhi-bin; Li, Xiao; Li, Jin-hua; Wang, Yan-chao
2015-05-01
In order to improve the accuracy and stability of the rebuilt spectrums, it is necessary that stability analysis and nicety measuring of the maximum optical path difference of interferograms in the photo-elastic modulator Fourier transform spectrometers(PEM-FTS). The maximum optical difference of interferograms is uncertain parameter, and it is relate to the resonant state, characteristic of frequency-thermal drift and driving voltage of PEM. Therefore, based on the principle of photo-elastic modulator Fourier transform interferometer, the model of the freguency-thermal drift is built, and the variety of the maximum optical path difference is analyzed; A measuring method of the maximum optical path difference is put forward, which is zero-crossing counting of laser's interference signal when the driving signal of PEM is as the standard. In the method the dual channel high-speed comparator and FPGA are used to transform sine wave to square wave, to realize zero-crossing trigger counting and errors compensation. On the condition that the 670. 8 nm laser is as the power source to produce the reference interferograms by the PEM interferometer, the 77. 471 µm maximum optical path difference could be measured by the zero-crossing counting the measuring errors is less than 0. 167 nm, the rebuilt spectral peak wavelength errors of the infrared blackbody is less than 2 nm. the result is content with PEM-FTS.
Maximum Principles for Discrete and Semidiscrete Reaction-Diffusion Equation
Petr Stehlík
2015-01-01
Full Text Available We study reaction-diffusion equations with a general reaction function f on one-dimensional lattices with continuous or discrete time ux′ (or Δtux=k(ux-1-2ux+ux+1+f(ux, x∈Z. We prove weak and strong maximum and minimum principles for corresponding initial-boundary value problems. Whereas the maximum principles in the semidiscrete case (continuous time exhibit similar features to those of fully continuous reaction-diffusion model, in the discrete case the weak maximum principle holds for a smaller class of functions and the strong maximum principle is valid in a weaker sense. We describe in detail how the validity of maximum principles depends on the nonlinearity and the time step. We illustrate our results on the Nagumo equation with the bistable nonlinearity.
Experimental study on prediction model for maximum rebound ratio
LEI Wei-dong; TENG Jun; A.HEFNY; ZHAO Jian; GUAN Jiong
2007-01-01
The proposed prediction model for estimating the maximum rebound ratio was applied to a field explosion test, Mandai test in Singapore.The estimated possible maximum Deak particle velocities(PPVs)were compared with the field records.Three of the four available field-recorded PPVs lie exactly below the estimated possible maximum values as expected.while the fourth available field-recorded PPV lies close to and a bit higher than the estimated maximum possible PPV The comparison results show that the predicted PPVs from the proposed prediction model for the maximum rebound ratio match the field.recorded PPVs better than those from two empirical formulae.The very good agreement between the estimated and field-recorded values validates the proposed prediction model for estimating PPV in a rock mass with a set of ipints due to application of a two dimensional compressional wave at the boundary of a tunnel or a borehole.
Pühringer, Gerald; Jakoby, Bernhard
2017-05-01
We evaluate a recently devised design of vertical-cavity enhanced resonant thermal emitter (VERTE) regarding stability to fabrication tolerances of PVD layer deposition techniques. Such an emitter achieves narrowband and coherent thermal emission and is composed of an multilayer stack of dielectric layers (silicon and silica) on top of a reflective metal (silver) structure. The silica layer above the metal acts as a vertical cavity enhancing the electromagnetic field between the reflective metal and the dielectric stack forming a Bragg mirror (1-D photonic crystal). In our previous work, we identified several suitable five-layer-stack configurations, which considered several features and limitations of a real-world device, such as temperature dependence of the materials, fabrication constraints or unwanted emission modes. However, the emission characteristics are very sensitive to the geometrical and optical properties of the material. In order to examine this behaviour, a Monte-Carlo algorithm was used to apply a Gauss-distributed error in depth (relative the unperturbed layer thickness) for every individual layer. The robustness of the emission properties against fabrication errors were evaluated and analyzed by significant statistical quantities. As expected, the main issue compromising the emission properties is a deviation of the resonance wavelength in relation to the initial target resonance wavelength of the unperturbed configuration. Interestingly, configurations with larger average layer thicknesses and therefore with larger absolute thickness deviations did not exhibit a larger variance of the emission wavelength. Instead, the variance slightly decreased or remained constant. A similar result was obtained for increasing the number of dielectric layers. In contrast, the peak emissivity (at normal incidence) was significantly influenced by the average layer depth of a configuration. Also, the effect of broadening of the spectral emittance curve due to
Izumida, Yuki; Okuda, Koji
2014-05-01
We formulate the work output and efficiency for linear irreversible heat engines working between a finite-sized hot heat source and an infinite-sized cold heat reservoir until the total system reaches the final thermal equilibrium state with a uniform temperature. We prove that when the heat engines operate at the maximum power under the tight-coupling condition without heat leakage the work output is just half of the exergy, which is known as the maximum available work extracted from a heat source. As a consequence, the corresponding efficiency is also half of its quasistatic counterpart.
Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications
Jia Chengchang
2010-01-01
Full Text Available Abstract Carbon nanotube–copper (CNT/Cu composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.
Thermal Properties of Carbon Nanotube–Copper Composites for Thermal Management Applications
2010-01-01
Carbon nanotube–copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications. PMID:20672107
Thermal Properties of Carbon Nanotube-Copper Composites for Thermal Management Applications
Chu, Ke; Guo, Hong; Jia, Chengchang; Yin, Fazhang; Zhang, Ximin; Liang, Xuebing; Chen, Hui
2010-05-01
Carbon nanotube-copper (CNT/Cu) composites have been successfully synthesized by means of a novel particles-compositing process followed by spark plasma sintering (SPS) technique. The thermal conductivity of the composites was measured by a laser flash technique and theoretical analyzed using an effective medium approach. The experimental results showed that the thermal conductivity unusually decreased after the incorporation of CNTs. Theoretical analyses revealed that the interfacial thermal resistance between the CNTs and the Cu matrix plays a crucial role in determining the thermal conductivity of bulk composites, and only small interfacial thermal resistance can induce a significant degradation in thermal conductivity for CNT/Cu composites. The influence of sintering condition on the thermal conductivity depended on the combined effects of multiple factors, i.e. porosity, CNTs distribution and CNT kinks or twists. The composites sintered at 600°C for 5 min under 50 MPa showed the maximum thermal conductivity. CNT/Cu composites are considered to be a promising material for thermal management applications.
2010-07-01
... as specified in 40 CFR 1065.610. This is the maximum in-use engine speed used for calculating the NOX... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the..., power density, and maximum in-use engine speed. 1042.140 Section 1042.140 Protection of...
Battery Thermal Characterization
Keyser, Matthew; Saxon, Aron; Powell, Mitchell; Shi, Ying
2016-06-07
This poster shows the progress in battery thermal characterization over the previous year. NREL collaborated with U.S. DRIVE and USABC battery developers to obtain thermal properties of their batteries, obtained heat capacity and heat generation of cells under various power profiles, obtained thermal images of the cells under various drive cycles, and used the measured results to validate thermal models. Thermal properties are used for the thermal analysis and design of improved battery thermal management systems to support achieve life and performance targets.
Stone, Wesley W.; Gilliom, Robert J.; Crawford, Charles G.
2008-01-01
Regression models were developed for predicting annual maximum and selected annual maximum moving-average concentrations of atrazine in streams using the Watershed Regressions for Pesticides (WARP) methodology developed by the National Water-Quality Assessment Program (NAWQA) of the U.S. Geological Survey (USGS). The current effort builds on the original WARP models, which were based on the annual mean and selected percentiles of the annual frequency distribution of atrazine concentrations. Estimates of annual maximum and annual maximum moving-average concentrations for selected durations are needed to characterize the levels of atrazine and other pesticides for comparison to specific water-quality benchmarks for evaluation of potential concerns regarding human health or aquatic life. Separate regression models were derived for the annual maximum and annual maximum 21-day, 60-day, and 90-day moving-average concentrations. Development of the regression models used the same explanatory variables, transformations, model development data, model validation data, and regression methods as those used in the original development of WARP. The models accounted for 72 to 75 percent of the variability in the concentration statistics among the 112 sampling sites used for model development. Predicted concentration statistics from the four models were within a factor of 10 of the observed concentration statistics for most of the model development and validation sites. Overall, performance of the models for the development and validation sites supports the application of the WARP models for predicting annual maximum and selected annual maximum moving-average atrazine concentration in streams and provides a framework to interpret the predictions in terms of uncertainty. For streams with inadequate direct measurements of atrazine concentrations, the WARP model predictions for the annual maximum and the annual maximum moving-average atrazine concentrations can be used to characterize
Maximum Likelihood Estimation of the Identification Parameters and Its Correction
无
2002-01-01
By taking the subsequence out of the input-output sequence of a system polluted by white noise, anindependent observation sequence and its probability density are obtained and then a maximum likelihood estimation of theidentification parameters is given. In order to decrease the asymptotic error, a corrector of maximum likelihood (CML)estimation with its recursive algorithm is given. It has been proved that the corrector has smaller asymptotic error thanthe least square methods. A simulation example shows that the corrector of maximum likelihood estimation is of higherapproximating precision to the true parameters than the least square methods.
Maximum frequency of the decametric radiation from Jupiter
Barrow, C. H.; Alexander, J. K.
1980-01-01
The upper frequency limits of Jupiter's decametric radio emission are found to be essentially the same when observed from the earth or, with considerably higher sensitivity, from the Voyager spacecraft close to Jupiter. This suggests that the maximum frequency is a real cut-off corresponding to a maximum gyrofrequency of about 38-40 MHz at Jupiter. It no longer appears to be necessary to specify different cut-off frequencies for the Io and non-Io emission as the maximum frequencies are roughly the same in each case.
Introduction to thermal transport
Simon R. Phillpot
2005-06-01
Full Text Available The relentless increase in the thermal loads imposed on devices and materials structures is driving renewed interest among materials scientists and engineers in the area of thermal transport. Applications include thermal barrier coatings on turbine blades, thermoelectric coolers, high-performance thermal transfer liquids, and heat dissipation in microelectronics. These, and other applications, demand not only ever more efficient thermal management, but also a better fundamental understanding of the underlying physical mechanisms.
Thermal analysis and design of passive solar buildings
Athienitis, AK
2013-01-01
Passive solar design techniques are becoming increasingly important in building design. This design reference book takes the building engineer or physicist step-by-step through the thermal analysis and design of passive solar buildings. In particular it emphasises two important topics: the maximum utilization of available solar energy and thermal storage, and the sizing of an appropriate auxiliary heating/cooling system in conjunction with good thermal control.Thermal Analysis and Design of Passive Solar Buildings is an important contribution towards the optimization of buildings as systems th
Photothermal characterization of thermally treated shells of Strombus Gigas
Hernández-Ayala, A.; Quintana, P.; Alvarado-Gil, J. J.; Aldana, D.
2005-06-01
The thermal properties of the marine shells of the mollusk Strombus gigas are studied using photoacoustic techniques. In order to generate changes in the layered structure of the shells, they were thermally treated in the range from ambient temperature up to 400ºC. Our results show that the thermal diffusivity and conductivity have a maximum at 200ºC due to the degradation of the organic matrix. At higher temperatures the thermal diffusivity and conductivity decrease due to the calcium carbonate structural phase transition from aragonite to calcite.
Thermal Management Architecture for Future Responsive Spacecraft
Bugby, D.; Zimbeck, W.; Kroliczek, E.
2009-03-01
This paper describes a novel thermal design architecture that enables satellites to be conceived, configured, launched, and operationally deployed very quickly. The architecture has been given the acronym SMARTS for Satellite Modular and Reconfigurable Thermal System and it involves four basic design rules: modest radiator oversizing, maximum external insulation, internal isothermalization and radiator heat flow modulation. The SMARTS philosophy is being developed in support of the DoD Operationally Responsive Space (ORS) initiative which seeks to drastically improve small satellite adaptability, deployability, and design flexibility. To illustrate the benefits of the philosophy for a prototypical multi-paneled small satellite, the paper describes a SMARTS thermal control system implementation that uses: panel-to-panel heat conduction, intra-panel heat pipe isothermalization, radiator heat flow modulation via a thermoelectric cooler (TEC) cold-biased loop heat pipe (LHP) and maximum external multi-layer insulation (MLI). Analyses are presented that compare the traditional "cold-biasing plus heater power" passive thermal design approach to the SMARTS approach. Plans for a 3-panel SMARTS thermal test bed are described. Ultimately, the goal is to incorporate SMARTS into the design of future ORS satellites, but it is also possible that some aspects of SMARTS technology could be used to improve the responsiveness of future NASA spacecraft. [22 CFR 125.4(b)(13) applicable
Hammerschmidt, Ulf; Hameury, Jacques; Strnad, Radek; Turzó-Andras, Emese; Wu, Jiyu
2015-07-01
This paper presents a critical review of current industrial techniques and instruments to measure the thermal conductivity of thermal insulation materials, especially those insulations that can operate at temperatures above and up to . These materials generally are of a porous nature. The measuring instruments dealt with here are selected based on their maximum working temperature that should be higher than at least . These instruments are special types of the guarded hot-plate apparatus, the guarded heat-flow meter, the transient hot-wire and hot-plane instruments as well as the laser/xenon flash devices. All technical characteristics listed are quoted from the generally accessible information of the relevant manufacturers. The paper includes rankings of the instruments according to their standard retail price, the maximum sample size, and maximum working temperature, as well as the minimum in their measurement range.
Dynamic thermal environment and thermal comfort.
Zhu, Y; Ouyang, Q; Cao, B; Zhou, X; Yu, J
2016-02-01
Research has shown that a stable thermal environment with tight temperature control cannot bring occupants more thermal comfort. Instead, such an environment will incur higher energy costs and produce greater CO2 emissions. Furthermore, this may lead to the degeneration of occupants' inherent ability to combat thermal stress, thereby weakening thermal adaptability. Measured data from many field investigations have shown that the human body has a higher acceptance to the thermal environment in free-running buildings than to that in air-conditioned buildings with similar average parameters. In naturally ventilated environments, occupants have reported superior thermal comfort votes and much greater thermal comfort temperature ranges compared to air-conditioned environments. This phenomenon is an integral part of the adaptive thermal comfort model. In addition, climate chamber experiments have proven that people prefer natural wind to mechanical wind in warm conditions; in other words, dynamic airflow can provide a superior cooling effect. However, these findings also indicate that significant questions related to thermal comfort remain unanswered. For example, what is the cause of these phenomena? How we can build a comfortable and healthy indoor environment for human beings? This article summarizes a series of research achievements in recent decades, tries to address some of these unanswered questions, and attempts to summarize certain problems for future research.
The Application of Maximum Principle in Supply Chain Cost Optimization
Zhou Ling; Wang Jun
2013-01-01
In this paper, using the maximum principle for analyzing dynamic cost, we propose a new two-stage supply chain model of the manufacturing-assembly mode for high-tech perishable products supply chain...
Maximum Principle for Nonlinear Cooperative Elliptic Systems on IR N
LEADI Liamidi; MARCOS Aboubacar
2011-01-01
We investigate in this work necessary and sufficient conditions for having a Maximum Principle for a cooperative elliptic system on the whole (IR)N.Moreover,we prove the existence of solutions by an approximation method for the considered system.
Maximum Likelihood Factor Structure of the Family Environment Scale.
Fowler, Patrick C.
1981-01-01
Presents the maximum likelihood factor structure of the Family Environment Scale. The first bipolar dimension, "cohesion v conflict," measures relationship-centered concerns, while the second unipolar dimension is an index of "organizational and control" activities. (Author)
Multiresolution maximum intensity volume rendering by morphological adjunction pyramids
Roerdink, Jos B.T.M.
We describe a multiresolution extension to maximum intensity projection (MIP) volume rendering, allowing progressive refinement and perfect reconstruction. The method makes use of morphological adjunction pyramids. The pyramidal analysis and synthesis operators are composed of morphological 3-D
Multiresolution Maximum Intensity Volume Rendering by Morphological Adjunction Pyramids
Roerdink, Jos B.T.M.
2001-01-01
We describe a multiresolution extension to maximum intensity projection (MIP) volume rendering, allowing progressive refinement and perfect reconstruction. The method makes use of morphological adjunction pyramids. The pyramidal analysis and synthesis operators are composed of morphological 3-D
Changes in context and perception of maximum reaching height.
Wagman, Jeffrey B; Day, Brian M
2014-01-01
Successfully performing a given behavior requires flexibility in both perception and behavior. In particular, doing so requires perceiving whether that behavior is possible across the variety of contexts in which it might be performed. Three experiments investigated how (changes in) context (ie point of observation and intended reaching task) influenced perception of maximum reaching height. The results of experiment 1 showed that perceived maximum reaching height more closely reflected actual reaching ability when perceivers occupied a point of observation that was compatible with that required for the reaching task. The results of experiments 2 and 3 showed that practice perceiving maximum reaching height from a given point of observation improved perception of maximum reaching height from a different point of observation, regardless of whether such practice occurred at a compatible or incompatible point of observation. In general, such findings show bounded flexibility in perception of affordances and are thus consistent with a description of perceptual systems as smart perceptual devices.
Water Quality Assessment and Total Maximum Daily Loads Information (ATTAINS)
U.S. Environmental Protection Agency — The Water Quality Assessment TMDL Tracking And Implementation System (ATTAINS) stores and tracks state water quality assessment decisions, Total Maximum Daily Loads...
Combining Experiments and Simulations Using the Maximum Entropy Principle
Boomsma, Wouter; Ferkinghoff-Borg, Jesper; Lindorff-Larsen, Kresten
2014-01-01
are not in quantitative agreement with experimental data. The principle of maximum entropy is a general procedure for constructing probability distributions in the light of new data, making it a natural tool in cases when an initial model provides results that are at odds with experiments. The number of maximum entropy...... in the context of a simple example, after which we proceed with a real-world application in the field of molecular simulations, where the maximum entropy procedure has recently provided new insight. Given the limited accuracy of force fields, macromolecular simulations sometimes produce results....... Three very recent papers have explored this problem using the maximum entropy approach, providing both new theoretical and practical insights to the problem. We highlight each of these contributions in turn and conclude with a discussion on remaining challenges....
On the sufficiency of the linear maximum principle
Vidal, Rene Victor Valqui
1987-01-01
Presents a family of linear maximum principles for the discrete-time optimal control problem, derived from the saddle-point theorem of mathematical programming. Some simple examples illustrate the applicability of the main theoretical results...
Maximum Photovoltaic Penetration Levels on Typical Distribution Feeders: Preprint
Hoke, A.; Butler, R.; Hambrick, J.; Kroposki, B.
2012-07-01
This paper presents simulation results for a taxonomy of typical distribution feeders with various levels of photovoltaic (PV) penetration. For each of the 16 feeders simulated, the maximum PV penetration that did not result in steady-state voltage or current violation is presented for several PV location scenarios: clustered near the feeder source, clustered near the midpoint of the feeder, clustered near the end of the feeder, randomly located, and evenly distributed. In addition, the maximum level of PV is presented for single, large PV systems at each location. Maximum PV penetration was determined by requiring that feeder voltages stay within ANSI Range A and that feeder currents stay within the ranges determined by overcurrent protection devices. Simulations were run in GridLAB-D using hourly time steps over a year with randomized load profiles based on utility data and typical meteorological year weather data. For 86% of the cases simulated, maximum PV penetration was at least 30% of peak load.
16 CFR 1505.8 - Maximum acceptable material temperatures.
2010-01-01
... Association, 155 East 44th Street, New York, NY 10017. Material Degrees C. Degrees F. Capacitors (1) (1) Class... capacitor has no marked temperature limit, the maximum acceptable temperature will be assumed to be 65...
Environmental Monitoring, Water Quality - Total Maximum Daily Load (TMDL)
NSGIC GIS Inventory (aka Ramona) — The Clean Water Act Section 303(d) establishes the Total Maximum Daily Load (TMDL) program. The purpose of the TMDL program is to identify sources of pollution and...
PREDICTION OF MAXIMUM DRY DENSITY OF LOCAL GRANULAR ...
methods. A test on a soil of relatively high solid density revealed that the developed relation looses ... where, Pd max is the laboratory maximum dry ... Addis-Jinima Road Rehabilitation. ..... data sets that differ considerably in the magnitude.
Environmental Monitoring, Water Quality - Total Maximum Daily Load (TMDL)
NSGIC Education | GIS Inventory — The Clean Water Act Section 303(d) establishes the Total Maximum Daily Load (TMDL) program. The purpose of the TMDL program is to identify sources of pollution and...
Solar Panel Maximum Power Point Tracker for Power Utilities
Sandeep Banik,
2014-01-01
Full Text Available ―Solar Panel Maximum Power Point Tracker For power utilities‖ As the name implied, it is a photovoltaic system that uses the photovoltaic array as a source of electrical power supply and since every photovoltaic (PV array has an optimum operating point, called the maximum power point, which varies depending on the insolation level and array voltage. A maximum power point tracker (MPPT is needed to operate the PV array at its maximum power point. The objective of this thesis project is to build a photovoltaic (PV array Of 121.6V DC Voltage(6 cell each 20V, 100watt And convert the DC voltage to Single phase 120v,50Hz AC voltage by switch mode power converter‘s and inverter‘s.
A Family of Maximum SNR Filters for Noise Reduction
Huang, Gongping; Benesty, Jacob; Long, Tao;
2014-01-01
This paper is devoted to the study and analysis of the maximum signal-to-noise ratio (SNR) filters for noise reduction both in the time and short-time Fourier transform (STFT) domains with one single microphone and multiple microphones. In the time domain, we show that the maximum SNR filters can...... significantly increase the SNR but at the expense of tremendous speech distortion. As a consequence, the speech quality improvement, measured by the perceptual evaluation of speech quality (PESQ) algorithm, is marginal if any, regardless of the number of microphones used. In the STFT domain, the maximum SNR....... This demonstrates that the maximum SNR filters, particularly the multichannel ones, in the STFT domain may be of great practical value....
Maximum likelihood estimation of finite mixture model for economic data
Phoong, Seuk-Yen; Ismail, Mohd Tahir
2014-06-01
Finite mixture model is a mixture model with finite-dimension. This models are provides a natural representation of heterogeneity in a finite number of latent classes. In addition, finite mixture models also known as latent class models or unsupervised learning models. Recently, maximum likelihood estimation fitted finite mixture models has greatly drawn statistician's attention. The main reason is because maximum likelihood estimation is a powerful statistical method which provides consistent findings as the sample sizes increases to infinity. Thus, the application of maximum likelihood estimation is used to fit finite mixture model in the present paper in order to explore the relationship between nonlinear economic data. In this paper, a two-component normal mixture model is fitted by maximum likelihood estimation in order to investigate the relationship among stock market price and rubber price for sampled countries. Results described that there is a negative effect among rubber price and stock market price for Malaysia, Thailand, Philippines and Indonesia.
Mattia M. Azzella
2014-03-01
Full Text Available Underwater light regime is widely considered the principal determinant of aquatic plant depth distribution. The majority of previous studies dealing with macrophytes in lakes have singled out Secchi disk transparency (SD values as the key empirical proxy to explain the maximum depth of macrophyte colonization (Zc. Few studies have investigated the role played by lake morphometry in structuring macrophyte beds. Using a balanced dataset including 20 Italian lakes (10 shallow and 10 deep lakes, we analysed transparency and lake morphometric traits to investigate their possible effects on Zc. Our results demonstrate that lake area plays a significant role, and confirm a direct influence of SD values on Zc. Considering lakes with an equal degree of transparency, smaller lakes may yield a lower Zc than larger ones. Morphology has a great influence on lake ecological characteristics especially on water thermal conditions and mixing depth. Based on our data, we argue that the thermal stratification plays a non negligible role in explaining macrophytes zonation, due to its influence on macrophytes life cycles and phytoplankton vertical distribution. Therefore, the present data suggest the need to enhance and refine our knowledge about the relationship between aquatic plants distribution and lake thermal conditions to better model the response of macrophytes to climate change and eutrophication.
Efficiency at and near maximum power of low-dissipation heat engines.
Holubec, Viktor; Ryabov, Artem
2015-11-01
A universality in optimization of trade-off between power and efficiency for low-dissipation Carnot cycles is presented. It is shown that any trade-off measure expressible in terms of efficiency and the ratio of power to its maximum value can be optimized independently of most details of the dynamics and of the coupling to thermal reservoirs. The result is demonstrated on two specific trade-off measures. The first one is designed for finding optimal efficiency for a given output power and clearly reveals diseconomy of engines working at maximum power. As the second example we derive universal lower and upper bounds on the efficiency at maximum trade-off given by the product of power and efficiency. The results are illustrated on a model of a diffusion-based heat engine. Such engines operate in the low-dissipation regime given that the used driving minimizes the work dissipated during the isothermal branches. The peculiarities of the corresponding optimization procedure are reviewed and thoroughly discussed.
Efficiency at and near maximum power of low-dissipation heat engines
Holubec, Viktor; Ryabov, Artem
2015-11-01
A universality in optimization of trade-off between power and efficiency for low-dissipation Carnot cycles is presented. It is shown that any trade-off measure expressible in terms of efficiency and the ratio of power to its maximum value can be optimized independently of most details of the dynamics and of the coupling to thermal reservoirs. The result is demonstrated on two specific trade-off measures. The first one is designed for finding optimal efficiency for a given output power and clearly reveals diseconomy of engines working at maximum power. As the second example we derive universal lower and upper bounds on the efficiency at maximum trade-off given by the product of power and efficiency. The results are illustrated on a model of a diffusion-based heat engine. Such engines operate in the low-dissipation regime given that the used driving minimizes the work dissipated during the isothermal branches. The peculiarities of the corresponding optimization procedure are reviewed and thoroughly discussed.
On the maximum sufficient range of interstellar vessels
Cartin, Daniel
2011-01-01
This paper considers the likely maximum range of space vessels providing the basis of a mature interstellar transportation network. Using the principle of sufficiency, it is argued that this range will be less than three parsecs for the average interstellar vessel. This maximum range provides access from the Solar System to a large majority of nearby stellar systems, with total travel distances within the network not excessively greater than actual physical distance.
Efficiency at Maximum Power of Interacting Molecular Machines
Golubeva, Natalia; Imparato, Alberto
2012-01-01
We investigate the efficiency of systems of molecular motors operating at maximum power. We consider two models of kinesin motors on a microtubule: for both the simplified and the detailed model, we find that the many-body exclusion effect enhances the efficiency at maximum power of the many- motor...... system, with respect to the single motor case. Remarkably, we find that this effect occurs in a limited region of the system parameters, compatible with the biologically relevant range....
Filtering Additive Measurement Noise with Maximum Entropy in the Mean
Gzyl, Henryk
2007-01-01
The purpose of this note is to show how the method of maximum entropy in the mean (MEM) may be used to improve parametric estimation when the measurements are corrupted by large level of noise. The method is developed in the context on a concrete example: that of estimation of the parameter in an exponential distribution. We compare the performance of our method with the bayesian and maximum likelihood approaches.
The maximum entropy production principle: two basic questions.
Martyushev, Leonid M
2010-05-12
The overwhelming majority of maximum entropy production applications to ecological and environmental systems are based on thermodynamics and statistical physics. Here, we discuss briefly maximum entropy production principle and raises two questions: (i) can this principle be used as the basis for non-equilibrium thermodynamics and statistical mechanics and (ii) is it possible to 'prove' the principle? We adduce one more proof which is most concise today.
A tropospheric ozone maximum over the equatorial Southern Indian Ocean
L. Zhang
2012-05-01
Full Text Available We examine the distribution of tropical tropospheric ozone (O_{3} from the Microwave Limb Sounder (MLS and the Tropospheric Emission Spectrometer (TES by using a global three-dimensional model of tropospheric chemistry (GEOS-Chem. MLS and TES observations of tropospheric O_{3} during 2005 to 2009 reveal a distinct, persistent O_{3} maximum, both in mixing ratio and tropospheric column, in May over the Equatorial Southern Indian Ocean (ESIO. The maximum is most pronounced in 2006 and 2008 and less evident in the other three years. This feature is also consistent with the total column O_{3} observations from the Ozone Mapping Instrument (OMI and the Atmospheric Infrared Sounder (AIRS. Model results reproduce the observed May O_{3} maximum and the associated interannual variability. The origin of the maximum reflects a complex interplay of chemical and dynamic factors. The O_{3} maximum is dominated by the O_{3} production driven by lightning nitrogen oxides (NO_{x} emissions, which accounts for 62% of the tropospheric column O_{3} in May 2006. We find the contribution from biomass burning, soil, anthropogenic and biogenic sources to the O_{3} maximum are rather small. The O_{3} productions in the lightning outflow from Central Africa and South America both peak in May and are directly responsible for the O_{3} maximum over the western ESIO. The lightning outflow from Equatorial Asia dominates over the eastern ESIO. The interannual variability of the O_{3} maximum is driven largely by the anomalous anti-cyclones over the southern Indian Ocean in May 2006 and 2008. The lightning outflow from Central Africa and South America is effectively entrained by the anti-cyclones followed by northward transport to the ESIO.
On the sufficiency of the linear maximum principle
Vidal, Rene Victor Valqui
1987-01-01
Presents a family of linear maximum principles for the discrete-time optimal control problem, derived from the saddle-point theorem of mathematical programming. Some simple examples illustrate the applicability of the main theoretical results......Presents a family of linear maximum principles for the discrete-time optimal control problem, derived from the saddle-point theorem of mathematical programming. Some simple examples illustrate the applicability of the main theoretical results...
Semidefinite Programming for Approximate Maximum Likelihood Sinusoidal Parameter Estimation
2009-01-01
We study the convex optimization approach for parameter estimation of several sinusoidal models, namely, single complex/real tone, multiple complex sinusoids, and single two-dimensional complex tone, in the presence of additive Gaussian noise. The major difficulty for optimally determining the parameters is that the corresponding maximum likelihood (ML) estimators involve finding the global minimum or maximum of multimodal cost functions because the frequencies are nonlinear in the observed s...
Hybrid TOA/AOA Approximate Maximum Likelihood Mobile Localization
Mohamed Zhaounia; Mohamed Adnan Landolsi; Ridha Bouallegue
2010-01-01
This letter deals with a hybrid time-of-arrival/angle-of-arrival (TOA/AOA) approximate maximum likelihood (AML) wireless location algorithm. Thanks to the use of both TOA/AOA measurements, the proposed technique can rely on two base stations (BS) only and achieves better performance compared to the original approximate maximum likelihood (AML) method. The use of two BSs is an important advantage in wireless cellular communication systems because it avoids hearability problems and reduces netw...
[Study on the maximum entropy principle and population genetic equilibrium].
Zhang, Hong-Li; Zhang, Hong-Yan
2006-03-01
A general mathematic model of population genetic equilibrium about one locus was constructed based on the maximum entropy principle by WANG Xiao-Long et al. They proved that the maximum solve of the model was just the frequency distribution that a population reached Hardy-Weinberg genetic equilibrium. It can suggest that a population reached Hardy-Weinberg genetic equilibrium when the genotype entropy of the population reached the maximal possible value, and that the frequency distribution of the maximum entropy was equivalent to the distribution of Hardy-Weinberg equilibrium law about one locus. They further assumed that the frequency distribution of the maximum entropy was equivalent to all genetic equilibrium distributions. This is incorrect, however. The frequency distribution of the maximum entropy was only equivalent to the distribution of Hardy-Weinberg equilibrium with respect to one locus or several limited loci. The case with regard to limited loci was proved in this paper. Finally we also discussed an example where the maximum entropy principle was not the equivalent of other genetic equilibria.
Thermal dynamics of bomb calorimeters
Lyon, Richard E.
2015-12-01
The thermal dynamics of bomb calorimeters are modeled using a lumped heat transfer analysis in which heat is released in a pressure vessel/bomb immersed in a stirred water bath that is surrounded by a static air space bounded by an insulated (static) jacket, a constant/controlled temperature jacket (isoperibol), or a changing temperature (adiabatic) jacket. The temperature history of the water bath for each of these boundary conditions (methods) is well described by the two-term solution for the calorimeter response to a heat impulse (combustion), allowing the heat transfer coefficients and thermal capacities of the bomb and water bath to be determined parametrically. The validated heat transfer model provides an expression for direct calculation of the heat released in an arbitrary process inside a bomb calorimeter using the temperature history of the water bath for each of the boundary conditions (methods). This result makes possible the direct calculation of the heat of combustion of a sample in an isoperibol calorimeter from the recorded temperature history without the need for semi-empirical temperature corrections to account for non-adiabatic behavior. Another useful result is that the maximum temperature rise of the water bath in the static jacket method is proportional to the total heat generated, and the empirical proportionality constant, which is determined by calibration, accounts for all of the heat losses and thermal lags of the calorimeter.
Enhancing radiative energy transfer through thermal extraction
Tan, Yixuan; Liu, Baoan; Shen, Sheng; Yu, Zongfu
2016-06-01
Thermal radiation plays an increasingly important role in many emerging energy technologies, such as thermophotovoltaics, passive radiative cooling and wearable cooling clothes [1]. One of the fundamental constraints in thermal radiation is the Stefan-Boltzmann law, which limits the maximum power of far-field radiation to P0 = σT4S, where σ is the Boltzmann constant, S and T are the area and the temperature of the emitter, respectively (Fig. 1a). In order to overcome this limit, it has been shown that near-field radiations could have an energy density that is orders of magnitude greater than the Stefan-Boltzmann law [2-7]. Unfortunately, such near-field radiation transfer is spatially confined and cannot carry radiative heat to the far field. Recently, a new concept of thermal extraction was proposed [8] to enhance far-field thermal emission, which, conceptually, operates on a principle similar to oil immersion lenses and light extraction in light-emitting diodes using solid immersion lens to increase light output [62].Thermal extraction allows a blackbody to radiate more energy to the far field than the apparent limit of the Stefan-Boltzmann law without breaking the second law of thermodynamics. Thermal extraction works by using a specially designed thermal extractor to convert and guide the near-field energy to the far field, as shown in Fig. 1b. The same blackbody as shown in Fig. 1a is placed closely below the thermal extractor with a spacing smaller than the thermal wavelength. The near-field coupling transfers radiative energy with a density greater than σT4. The thermal extractor, made from transparent and high-index or structured materials, does not emit or absorb any radiation. It transforms the near-field energy and sends it toward the far field. As a result, the total amount of far-field radiative heat dissipated by the same blackbody is greatly enhanced above SσT4, where S is the area of the emitter. This paper will review the progress in thermal
Thermal performance optimization of a flat plate solar air heater using genetic algorithm
Varun; Siddhartha [Department of Mechanical Engineering, National Institute of Technology, Hamirpur 177 005 (H.P.) (India)
2010-05-15
Thermal performance of solar air heater is low and different techniques are adopted to increase the performance of solar air heaters, such as: fins, artificial roughness etc. In this paper an attempt has been done to optimize the thermal performance of flat plate solar air heater by considering the different system and operating parameters to obtain maximum thermal performance. Thermal performance is obtained for different Reynolds number, emissivity of the plate, tilt angle and number of glass plates by using genetic algorithm. (author)
Thermal ecology of the fiddler crab Uca panacea: Thermal constraints and organismal responses.
Darnell, M Zachary; Nicholson, Haley S; Munguia, Pablo
2015-08-01
Temperature is one of the primary environmental variables limiting organismal performance, fitness, and species distributions. Yet, understanding temperature effects requires thorough exploration of thermal constraints and organismal responses that can translate to fitness and non-lethal long-term consequences under both constant and changing thermal regimes. We examined the thermal ecology of the fiddler crab Uca panacea, including critical thermal limits, thermal sensitivity of locomotion, operative environmental temperatures, preferred body temperatures, and acclimation ability. Operative environmental temperatures frequently reached the critical thermal maximum (41.8±0.8°C, mean ± s.e.m.), especially in unvegetated microhabitats, indicating the need for behavioral thermoregulation to maintain diurnal activity patterns. Preferred body temperatures (21.1-28.6°C) were substantially below the thermal optimum (30-40°C), although further research is needed to determine the driver of this mismatch. Critical thermal limits shifted 2-4°C in response to exposure to low (20°C) or high (35°C) temperatures, with full acclimation occurring in approximately 9d. This capacity for rapid acclimation, combined with the capacity for behavioral thermoregulation, is a strong candidate mechanism that explains the broad habitat use and could help explain the successful pantropical distribution of fiddler crabs. Copyright © 2015 Elsevier Ltd. All rights reserved.
Thermal diffusivity effect in opto-thermal skin measurements
Xiao, P; Imhof, R E [Faculty of ESBE, London South Bank University, 103 Borough Road, London SE1 0AA (United Kingdom); Cui, Y [Sunrise Systems Limited, Flint Bridge Business Centre, Ely Road, Waterbeach, Cambridge CB5 9QZ (United Kingdom); Ciortea, L I; Berg, E P, E-mail: xiaop@lsbu.ac.u [Biox Systems Ltd, 103 Borough Road, London SE1 0AA (United Kingdom)
2010-03-01
We present our latest study on the thermal diffusivity effect in opto-thermal skin measurements. We discuss how thermal diffusivity affects the shape of opto-thermal signal, and how to measure thermal diffusivity in opto-thermal measurements of arbitrary sample surfaces. We also present a mathematical model for a thermally gradient material, and its corresponding opto-thermal signal. Finally, we show some of our latest experimental results of this thermal diffusivity effect study.
Inhomogeneous thermal conductivity enhances thermoelectric cooling
Tingyu Lu
2014-12-01
Full Text Available We theoretically investigate the enhancement of thermoelectric cooling performance in thermoelectric refrigerators made of materials with inhomogeneous thermal conductivity, beyond the usual practice of enhancing thermoelectric figure of merit (ZT of materials. The dissipation of the Joule heat in such thermoelectric refrigerators is asymmetric which can give rise to better thermoelectric cooling performance. Although the thermoelectric figure of merit and the coefficient-of-performance are slightly enhanced, both the maximum cooling power and the maximum cooling temperature difference can be enhanced significantly. This finding can be used to increase the heat absorption at the cold end. We further find that the asymmetric dissipation of Joule heat leads to thermal rectification.
Kuracina Richard
2015-06-01
Full Text Available The article deals with the measurement of maximum explosion pressure and the maximum rate of exposure pressure rise of wood dust cloud. The measurements were carried out according to STN EN 14034-1+A1:2011 Determination of explosion characteristics of dust clouds. Part 1: Determination of the maximum explosion pressure pmax of dust clouds and the maximum rate of explosion pressure rise according to STN EN 14034-2+A1:2012 Determination of explosion characteristics of dust clouds - Part 2: Determination of the maximum rate of explosion pressure rise (dp/dtmax of dust clouds. The wood dust cloud in the chamber is achieved mechanically. The testing of explosions of wood dust clouds showed that the maximum value of the pressure was reached at the concentrations of 450 g / m3 and its value is 7.95 bar. The fastest increase of pressure was observed at the concentrations of 450 g / m3 and its value was 68 bar / s.
Individual Module Maximum Power Point Tracking for Thermoelectric Generator Systems
Vadstrup, Casper; Schaltz, Erik; Chen, Min
2013-07-01
In a thermoelectric generator (TEG) system the DC/DC converter is under the control of a maximum power point tracker which ensures that the TEG system outputs the maximum possible power to the load. However, if the conditions, e.g., temperature, health, etc., of the TEG modules are different, each TEG module will not produce its maximum power. If each TEG module is controlled individually, each TEG module can be operated at its maximum power point and the TEG system output power will therefore be higher. In this work a power converter based on noninverting buck-boost converters capable of handling four TEG modules is presented. It is shown that, when each module in the TEG system is operated under individual maximum power point tracking, the system output power for this specific application can be increased by up to 8.4% relative to the situation when the modules are connected in series and 16.7% relative to the situation when the modules are connected in parallel.
Size dependence of efficiency at maximum power of heat engine
Izumida, Y.
2013-10-01
We perform a molecular dynamics computer simulation of a heat engine model to study how the engine size difference affects its performance. Upon tactically increasing the size of the model anisotropically, we determine that there exists an optimum size at which the model attains the maximum power for the shortest working period. This optimum size locates between the ballistic heat transport region and the diffusive heat transport one. We also study the size dependence of the efficiency at the maximum power. Interestingly, we find that the efficiency at the maximum power around the optimum size attains a value that has been proposed as a universal upper bound, and it even begins to exceed the bound as the size further increases. We explain this behavior of the efficiency at maximum power by using a linear response theory for the heat engine operating under a finite working period, which naturally extends the low-dissipation Carnot cycle model [M. Esposito, R. Kawai, K. Lindenberg, C. Van den Broeck, Phys. Rev. Lett. 105, 150603 (2010)]. The theory also shows that the efficiency at the maximum power under an extreme condition may reach the Carnot efficiency in principle.© EDP Sciences Società Italiana di Fisica Springer-Verlag 2013.
How long do centenarians survive? Life expectancy and maximum lifespan.
Modig, K; Andersson, T; Vaupel, J; Rau, R; Ahlbom, A
2017-08-01
The purpose of this study was to explore the pattern of mortality above the age of 100 years. In particular, we aimed to examine whether Scandinavian data support the theory that mortality reaches a plateau at particularly old ages. Whether the maximum length of life increases with time was also investigated. The analyses were based on individual level data on all Swedish and Danish centenarians born from 1870 to 1901; in total 3006 men and 10 963 women were included. Birth cohort-specific probabilities of dying were calculated. Exact ages were used for calculations of maximum length of life. Whether maximum age changed over time was analysed taking into account increases in cohort size. The results confirm that there has not been any improvement in mortality amongst centenarians in the past 30 years and that the current rise in life expectancy is driven by reductions in mortality below the age of 100 years. The death risks seem to reach a plateau of around 50% at the age 103 years for men and 107 years for women. Despite the rising life expectancy, the maximum age does not appear to increase, in particular after accounting for the increasing number of individuals of advanced age. Mortality amongst centenarians is not changing despite improvements at younger ages. An extension of the maximum lifespan and a sizeable extension of life expectancy both require reductions in mortality above the age of 100 years. © 2017 The Association for the Publication of the Journal of Internal Medicine.
Predicting species' maximum dispersal distances from simple plant traits.
Tamme, Riin; Götzenberger, Lars; Zobel, Martin; Bullock, James M; Hooftman, Danny A P; Kaasik, Ants; Pärtel, Meelis
2014-02-01
Many studies have shown plant species' dispersal distances to be strongly related to life-history traits, but how well different traits can predict dispersal distances is not yet known. We used cross-validation techniques and a global data set (576 plant species) to measure the predictive power of simple plant traits to estimate species' maximum dispersal distances. Including dispersal syndrome (wind, animal, ant, ballistic, and no special syndrome), growth form (tree, shrub, herb), seed mass, seed release height, and terminal velocity in different combinations as explanatory variables we constructed models to explain variation in measured maximum dispersal distances and evaluated their power to predict maximum dispersal distances. Predictions are more accurate, but also limited to a particular set of species, if data on more specific traits, such as terminal velocity, are available. The best model (R2 = 0.60) included dispersal syndrome, growth form, and terminal velocity as fixed effects. Reasonable predictions of maximum dispersal distance (R2 = 0.53) are also possible when using only the simplest and most commonly measured traits; dispersal syndrome and growth form together with species taxonomy data. We provide a function (dispeRsal) to be run in the software package R. This enables researchers to estimate maximum dispersal distances with confidence intervals for plant species using measured traits as predictors. Easily obtainable trait data, such as dispersal syndrome (inferred from seed morphology) and growth form, enable predictions to be made for a large number of species.
Prediction of three dimensional maximum isometric neck strength.
Fice, Jason B; Siegmund, Gunter P; Blouin, Jean-Sébastien
2014-09-01
We measured maximum isometric neck strength under combinations of flexion/extension, lateral bending and axial rotation to determine whether neck strength in three dimensions (3D) can be predicted from principal axes strength. This would allow biomechanical modelers to validate their neck models across many directions using only principal axis strength data. Maximum isometric neck moments were measured in 9 male volunteers (29±9 years) for 17 directions. The 3D moments were normalized by the principal axis moments, and compared to unity for all directions tested. Finally, each subject's maximum principal axis moments were used to predict their resultant moment in the off-axis directions. Maximum moments were 30±6 N m in flexion, 32±9 N m in lateral bending, 51±11 N m in extension, and 13±5 N m in axial rotation. The normalized 3D moments were not significantly different from unity (95% confidence interval contained one), except for three directions that combined ipsilateral axial rotation and lateral bending; in these directions the normalized moments exceeded one. Predicted resultant moments compared well to the actual measured values (r2=0.88). Despite exceeding unity, the normalized moments were consistent across subjects to allow prediction of maximum 3D neck strength using principal axes neck strength.
Ouellette Thermal Test Facility
Federal Laboratory Consortium — The Thermal Test Facility is a joint Army/Navy state-of-the-art facility (8,100 ft2) that was designed to:Evaluate and characterize the effect of flame and thermal...
Solar Thermal Rocket Propulsion
Sercel, J. C.
1986-01-01
Paper analyzes potential of solar thermal rockets as means of propulsion for planetary spacecraft. Solar thermal rocket uses concentrated Sunlight to heat working fluid expelled through nozzle to produce thrust.
Ouellette Thermal Test Facility
Federal Laboratory Consortium — The Thermal Test Facility is a joint Army/Navy state-of-the-art facility (8,100 ft2) that was designed to: Evaluate and characterize the effect of flame and thermal...
Chemical enhancement of fingermark in blood on thermal paper.
Hong, Sungwook; Seo, Jin Yi
2015-12-01
Chemical enhancement methods for fingermark in blood deposited on the surface of a thermal paper substrate were examined. The blood-sensitive reagents compared were LCV (leuco crystal violet), Amido black and Hungarian red. Fingermark in blood on the surface of thermal paper can be fixed with 2% 5-sulfosalicylic acid solution. LCV was found as an inadequate blood staining reagent because of bubbling, diffusion, and blurring on the surface of thermal paper. Hungarian red was also an inadequate blood staining reagent because excess Hungarian red on the surface of thermal paper was not washed away in the de-staining procedure. Amido black was the best staining reagent among three staining reagents compared. The maximum dilution ratio visible to the naked eye after Amido black staining was 1 in 80 for the thermally sensitive surface and 1 in 20 for the thermally non-sensitive surface.
REACTOR GROUT THERMAL PROPERTIES
Steimke, J.; Qureshi, Z.; Restivo, M.; Guerrero, H.
2011-01-28
Savannah River Site has five dormant nuclear production reactors. Long term disposition will require filling some reactor buildings with grout up to ground level. Portland cement based grout will be used to fill the buildings with the exception of some reactor tanks. Some reactor tanks contain significant quantities of aluminum which could react with Portland cement based grout to form hydrogen. Hydrogen production is a safety concern and gas generation could also compromise the structural integrity of the grout pour. Therefore, it was necessary to develop a non-Portland cement grout to fill reactors that contain significant quantities of aluminum. Grouts generate heat when they set, so the potential exists for large temperature increases in a large pour, which could compromise the integrity of the pour. The primary purpose of the testing reported here was to measure heat of hydration, specific heat, thermal conductivity and density of various reactor grouts under consideration so that these properties could be used to model transient heat transfer for different pouring strategies. A secondary purpose was to make qualitative judgments of grout pourability and hardened strength. Some reactor grout formulations were unacceptable because they generated too much heat, or started setting too fast, or required too long to harden or were too weak. The formulation called 102H had the best combination of characteristics. It is a Calcium Alumino-Sulfate grout that contains Ciment Fondu (calcium aluminate cement), Plaster of Paris (calcium sulfate hemihydrate), sand, Class F fly ash, boric acid and small quantities of additives. This composition afforded about ten hours of working time. Heat release began at 12 hours and was complete by 24 hours. The adiabatic temperature rise was 54 C which was within specification. The final product was hard and displayed no visible segregation. The density and maximum particle size were within specification.
Predicting Maximum Sunspot Number in Solar Cycle 24
Nipa J Bhatt; Rajmal Jain; Malini Aggarwal
2009-03-01
A few prediction methods have been developed based on the precursor technique which is found to be successful for forecasting the solar activity. Considering the geomagnetic activity aa indices during the descending phase of the preceding solar cycle as the precursor, we predict the maximum amplitude of annual mean sunspot number in cycle 24 to be 111 ± 21. This suggests that the maximum amplitude of the upcoming cycle 24 will be less than cycles 21–22. Further, we have estimated the annual mean geomagnetic activity aa index for the solar maximum year in cycle 24 to be 20.6 ± 4.7 and the average of the annual mean sunspot number during the descending phase of cycle 24 is estimated to be 48 ± 16.8.
Construction and enumeration of Boolean functions with maximum algebraic immunity
ZHANG WenYing; WU ChuanKun; LIU XiangZhong
2009-01-01
Algebraic immunity is a new cryptographic criterion proposed against algebraic attacks. In order to resist algebraic attacks, Boolean functions used in many stream ciphers should possess high algebraic immunity. This paper presents two main results to find balanced Boolean functions with maximum algebraic immunity. Through swapping the values of two bits, and then generalizing the result to swap some pairs of bits of the symmetric Boolean function constructed by Dalai, a new class of Boolean functions with maximum algebraic immunity are constructed. Enumeration of such functions is also given. For a given function p(x) with deg(p(x)) < [n/2], we give a method to construct functions in the form p(x)+q(x) which achieve the maximum algebraic immunity, where every term with nonzero coefficient in the ANF of q(x) has degree no less than [n/2].
Propane spectral resolution enhancement by the maximum entropy method
Bonavito, N. L.; Stewart, K. P.; Hurley, E. J.; Yeh, K. C.; Inguva, R.
1990-01-01
The Burg algorithm for maximum entropy power spectral density estimation is applied to a time series of data obtained from a Michelson interferometer and compared with a standard FFT estimate for resolution capability. The propane transmittance spectrum was estimated by use of the FFT with a 2 to the 18th data sample interferogram, giving a maximum unapodized resolution of 0.06/cm. This estimate was then interpolated by zero filling an additional 2 to the 18th points, and the final resolution was taken to be 0.06/cm. Comparison of the maximum entropy method (MEM) estimate with the FFT was made over a 45/cm region of the spectrum for several increasing record lengths of interferogram data beginning at 2 to the 10th. It is found that over this region the MEM estimate with 2 to the 16th data samples is in close agreement with the FFT estimate using 2 to the 18th samples.
Mass mortality of the vermetid gastropod Ceraesignum maximum
Brown, A. L.; Frazer, T. K.; Shima, J. S.; Osenberg, C. W.
2016-09-01
Ceraesignum maximum (G.B. Sowerby I, 1825), formerly Dendropoma maximum, was subject to a sudden, massive die-off in the Society Islands, French Polynesia, in 2015. On Mo'orea, where we have detailed documentation of the die-off, these gastropods were previously found in densities up to 165 m-2. In July 2015, we surveyed shallow back reefs of Mo'orea before, during and after the die-off, documenting their swift decline. All censused populations incurred 100% mortality. Additional surveys and observations from Mo'orea, Tahiti, Bora Bora, and Huahine (but not Taha'a) suggested a similar, and approximately simultaneous, die-off. The cause(s) of this cataclysmic mass mortality are currently unknown. Given the previously documented negative effects of C. maximum on corals, we expect the die-off will have cascading effects on the reef community.
The optimal polarizations for achieving maximum contrast in radar images
Swartz, A. A.; Yueh, H. A.; Kong, J. A.; Novak, L. M.; Shin, R. T.
1988-01-01
There is considerable interest in determining the optimal polarizations that maximize contrast between two scattering classes in polarimetric radar images. A systematic approach is presented for obtaining the optimal polarimetric matched filter, i.e., that filter which produces maximum contrast between two scattering classes. The maximization procedure involves solving an eigenvalue problem where the eigenvector corresponding to the maximum contrast ratio is an optimal polarimetric matched filter. To exhibit the physical significance of this filter, it is transformed into its associated transmitting and receiving polarization states, written in terms of horizontal and vertical vector components. For the special case where the transmitting polarization is fixed, the receiving polarization which maximizes the contrast ratio is also obtained. Polarimetric filtering is then applies to synthetic aperture radar images obtained from the Jet Propulsion Laboratory. It is shown, both numerically and through the use of radar imagery, that maximum image contrast can be realized when data is processed with the optimal polarimeter matched filter.
Penalized maximum likelihood estimation and variable selection in geostatistics
Chu, Tingjin; Wang, Haonan; 10.1214/11-AOS919
2012-01-01
We consider the problem of selecting covariates in spatial linear models with Gaussian process errors. Penalized maximum likelihood estimation (PMLE) that enables simultaneous variable selection and parameter estimation is developed and, for ease of computation, PMLE is approximated by one-step sparse estimation (OSE). To further improve computational efficiency, particularly with large sample sizes, we propose penalized maximum covariance-tapered likelihood estimation (PMLE$_{\\mathrm{T}}$) and its one-step sparse estimation (OSE$_{\\mathrm{T}}$). General forms of penalty functions with an emphasis on smoothly clipped absolute deviation are used for penalized maximum likelihood. Theoretical properties of PMLE and OSE, as well as their approximations PMLE$_{\\mathrm{T}}$ and OSE$_{\\mathrm{T}}$ using covariance tapering, are derived, including consistency, sparsity, asymptotic normality and the oracle properties. For covariance tapering, a by-product of our theoretical results is consistency and asymptotic normal...
Influence of maximum decking charge on intensity of blasting vibration
无
2006-01-01
Based on the character of short-time non-stationary random signal, the relationship between the maximum decking charge and energy distribution of blasting vibration signals was investigated by means of the wavelet packet method. Firstly, the characteristics of wavelet transform and wavelet packet analysis were described. Secondly, the blasting vibration signals were analyzed by wavelet packet based on software MATLAB, and the change of energy distribution curve at different frequency bands were obtained. Finally, the law of energy distribution of blasting vibration signals changing with the maximum decking charge was analyzed. The results show that with the increase of decking charge, the ratio of the energy of high frequency to total energy decreases, the dominant frequency bands of blasting vibration signals tend towards low frequency and blasting vibration does not depend on the maximum decking charge.
The subsequence weight distribution of summed maximum length digital sequences
Weathers, G. D.; Graf, E. R.; Wallace, G. R.
1974-01-01
An attempt is made to develop mathematical formulas to provide the basis for the design of pseudorandom signals intended for applications requiring accurate knowledge of the statistics of the signals. The analysis approach involves calculating the first five central moments of the weight distribution of subsequences of hybrid-sum sequences. The hybrid-sum sequence is formed from the modulo-two sum of k maximum length sequences and is an extension of the sum sequences formed from two maximum length sequences that Gilson (1966) evaluated. The weight distribution of the subsequences serves as an approximation to the filtering process. The basic reason for the analysis of hybrid-sum sequences is to establish a large group of sequences with good statistical properties. It is shown that this can be accomplished much more efficiently using the hybrid-sum approach rather than forming the group strictly from maximum length sequences.
Maximum power point tracking for optimizing energy harvesting process
Akbari, S.; Thang, P. C.; Veselov, D. S.
2016-10-01
There has been a growing interest in using energy harvesting techniques for powering wireless sensor networks. The reason for utilizing this technology can be explained by the sensors limited amount of operation time which results from the finite capacity of batteries and the need for having a stable power supply in some applications. Energy can be harvested from the sun, wind, vibration, heat, etc. It is reasonable to develop multisource energy harvesting platforms for increasing the amount of harvesting energy and to mitigate the issue concerning the intermittent nature of ambient sources. In the context of solar energy harvesting, it is possible to develop algorithms for finding the optimal operation point of solar panels at which maximum power is generated. These algorithms are known as maximum power point tracking techniques. In this article, we review the concept of maximum power point tracking and provide an overview of the research conducted in this area for wireless sensor networks applications.
Proscriptive Bayesian Programming and Maximum Entropy: a Preliminary Study
Koike, Carla Cavalcante
2008-11-01
Some problems found in robotics systems, as avoiding obstacles, can be better described using proscriptive commands, where only prohibited actions are indicated in contrast to prescriptive situations, which demands that a specific command be specified. An interesting question arises regarding the possibility to learn automatically if proscriptive commands are suitable and which parametric function could be better applied. Lately, a great variety of problems in robotics domain are object of researches using probabilistic methods, including the use of Maximum Entropy in automatic learning for robot control systems. This works presents a preliminary study on automatic learning of proscriptive robot control using maximum entropy and using Bayesian Programming. It is verified whether Maximum entropy and related methods can favour proscriptive commands in an obstacle avoidance task executed by a mobile robot.
Multitime maximum principle approach of minimal submanifolds and harmonic maps
Udriste, Constantin
2011-01-01
Some optimization problems coming from the Differential Geometry, as for example, the minimal submanifolds problem and the harmonic maps problem are solved here via interior solutions of appropriate multitime optimal control problems. Section 1 underlines some science domains where appear multitime optimal control problems. Section 2 (Section 3) recalls the multitime maximum principle for optimal control problems with multiple (curvilinear) integral cost functionals and $m$-flow type constraint evolution. Section 4 shows that there exists a multitime maximum principle approach of multitime variational calculus. Section 5 (Section 6) proves that the minimal submanifolds (harmonic maps) are optimal solutions of multitime evolution PDEs in an appropriate multitime optimal control problem. Section 7 uses the multitime maximum principle to show that of all solids having a given surface area, the sphere is the one having the greatest volume. Section 8 studies the minimal area of a multitime linear flow as optimal c...
A Maximum Entropy Estimator for the Aggregate Hierarchical Logit Model
Pedro Donoso
2011-08-01
Full Text Available A new approach for estimating the aggregate hierarchical logit model is presented. Though usually derived from random utility theory assuming correlated stochastic errors, the model can also be derived as a solution to a maximum entropy problem. Under the latter approach, the Lagrange multipliers of the optimization problem can be understood as parameter estimators of the model. Based on theoretical analysis and Monte Carlo simulations of a transportation demand model, it is demonstrated that the maximum entropy estimators have statistical properties that are superior to classical maximum likelihood estimators, particularly for small or medium-size samples. The simulations also generated reduced bias in the estimates of the subjective value of time and consumer surplus.
Approximate maximum-entropy moment closures for gas dynamics
McDonald, James G.
2016-11-01
Accurate prediction of flows that exist between the traditional continuum regime and the free-molecular regime have proven difficult to obtain. Current methods are either inaccurate in this regime or prohibitively expensive for practical problems. Moment closures have long held the promise of providing new, affordable, accurate methods in this regime. The maximum-entropy hierarchy of closures seems to offer particularly attractive physical and mathematical properties. Unfortunately, several difficulties render the practical implementation of maximum-entropy closures very difficult. This work examines the use of simple approximations to these maximum-entropy closures and shows that physical accuracy that is vastly improved over continuum methods can be obtained without a significant increase in computational cost. Initially the technique is demonstrated for a simple one-dimensional gas. It is then extended to the full three-dimensional setting. The resulting moment equations are used for the numerical solution of shock-wave profiles with promising results.
Semidefinite Programming for Approximate Maximum Likelihood Sinusoidal Parameter Estimation
Kenneth W. K. Lui
2009-01-01
Full Text Available We study the convex optimization approach for parameter estimation of several sinusoidal models, namely, single complex/real tone, multiple complex sinusoids, and single two-dimensional complex tone, in the presence of additive Gaussian noise. The major difficulty for optimally determining the parameters is that the corresponding maximum likelihood (ML estimators involve finding the global minimum or maximum of multimodal cost functions because the frequencies are nonlinear in the observed signals. By relaxing the nonconvex ML formulations using semidefinite programs, high-fidelity approximate solutions are obtained in a globally optimum fashion. Computer simulations are included to contrast the estimation performance of the proposed semi-definite relaxation methods with the iterative quadratic maximum likelihood technique as well as Cramér-Rao lower bound.
Remarks on the strong maximum principle for nonlocal operators
Jerome Coville
2008-05-01
Full Text Available In this note, we study the existence of a strong maximum principle for the nonlocal operator $$ mathcal{M}[u](x :=int_{G}J(gu(x*g^{-1}dmu(g - u(x, $$ where $G$ is a topological group acting continuously on a Hausdorff space $X$ and $u in C(X$. First we investigate the general situation and derive a pre-maximum principle. Then we restrict our analysis to the case of homogeneous spaces (i.e., $ X=G /H$. For such Hausdorff spaces, depending on the topology, we give a condition on $J$ such that a strong maximum principle holds for $mathcal{M}$. We also revisit the classical case of the convolution operator (i.e. $G=(mathbb{R}^n,+, X=mathbb{R}^n, dmu =dy$.
Resource-constrained maximum network throughput on space networks
Yanling Xing; Ning Ge; Youzheng Wang
2015-01-01
This paper investigates the maximum network through-put for resource-constrained space networks based on the delay and disruption-tolerant networking (DTN) architecture. Specifical y, this paper proposes a methodology for calculating the maximum network throughput of multiple transmission tasks under storage and delay constraints over a space network. A mixed-integer linear programming (MILP) is formulated to solve this problem. Simula-tions results show that the proposed methodology can successful y calculate the optimal throughput of a space network under storage and delay constraints, as wel as a clear, monotonic relationship between end-to-end delay and the maximum network throughput under storage constraints. At the same time, the optimization re-sults shine light on the routing and transport protocol design in space communication, which can be used to obtain the optimal network throughput.
Semidefinite Programming for Approximate Maximum Likelihood Sinusoidal Parameter Estimation
Lui, Kenneth W. K.; So, H. C.
2009-12-01
We study the convex optimization approach for parameter estimation of several sinusoidal models, namely, single complex/real tone, multiple complex sinusoids, and single two-dimensional complex tone, in the presence of additive Gaussian noise. The major difficulty for optimally determining the parameters is that the corresponding maximum likelihood (ML) estimators involve finding the global minimum or maximum of multimodal cost functions because the frequencies are nonlinear in the observed signals. By relaxing the nonconvex ML formulations using semidefinite programs, high-fidelity approximate solutions are obtained in a globally optimum fashion. Computer simulations are included to contrast the estimation performance of the proposed semi-definite relaxation methods with the iterative quadratic maximum likelihood technique as well as Cramér-Rao lower bound.
Quality, precision and accuracy of the maximum No. 40 anemometer
Obermeir, J. [Otech Engineering, Davis, CA (United States); Blittersdorf, D. [NRG Systems Inc., Hinesburg, VT (United States)
1996-12-31
This paper synthesizes available calibration data for the Maximum No. 40 anemometer. Despite its long history in the wind industry, controversy surrounds the choice of transfer function for this anemometer. Many users are unaware that recent changes in default transfer functions in data loggers are producing output wind speed differences as large as 7.6%. Comparison of two calibration methods used for large samples of Maximum No. 40 anemometers shows a consistent difference of 4.6% in output speeds. This difference is significantly larger than estimated uncertainty levels. Testing, initially performed to investigate related issues, reveals that Gill and Maximum cup anemometers change their calibration transfer functions significantly when calibrated in the open atmosphere compared with calibration in a laminar wind tunnel. This indicates that atmospheric turbulence changes the calibration transfer function of cup anemometers. These results call into question the suitability of standard wind tunnel calibration testing for cup anemometers. 6 refs., 10 figs., 4 tabs.
The evolution of maximum body size of terrestrial mammals.
Smith, Felisa A; Boyer, Alison G; Brown, James H; Costa, Daniel P; Dayan, Tamar; Ernest, S K Morgan; Evans, Alistair R; Fortelius, Mikael; Gittleman, John L; Hamilton, Marcus J; Harding, Larisa E; Lintulaakso, Kari; Lyons, S Kathleen; McCain, Christy; Okie, Jordan G; Saarinen, Juha J; Sibly, Richard M; Stephens, Patrick R; Theodor, Jessica; Uhen, Mark D
2010-11-26
The extinction of dinosaurs at the Cretaceous/Paleogene (K/Pg) boundary was the seminal event that opened the door for the subsequent diversification of terrestrial mammals. Our compilation of maximum body size at the ordinal level by sub-epoch shows a near-exponential increase after the K/Pg. On each continent, the maximum size of mammals leveled off after 40 million years ago and thereafter remained approximately constant. There was remarkable congruence in the rate, trajectory, and upper limit across continents, orders, and trophic guilds, despite differences in geological and climatic history, turnover of lineages, and ecological variation. Our analysis suggests that although the primary driver for the evolution of giant mammals was diversification to fill ecological niches, environmental temperature and land area may have ultimately constrained the maximum size achieved.
The maximum force in a column under constant speed compression
Kuzkin, Vitaly A
2015-01-01
Dynamic buckling of an elastic column under compression at constant speed is investigated assuming the first-mode buckling. Two cases are considered: (i) an imperfect column (Hoff's statement), and (ii) a perfect column having an initial lateral deflection. The range of parameters, where the maximum load supported by a column exceeds Euler static force is determined. In this range, the maximum load is represented as a function of the compression rate, slenderness ratio, and imperfection/initial deflection. Considering the results we answer the following question: "How slowly the column should be compressed in order to measure static load-bearing capacity?" This question is important for the proper setup of laboratory experiments and computer simulations of buckling. Additionally, it is shown that the behavior of a perfect column having an initial deflection differ significantlys form the behavior of an imperfect column. In particular, the dependence of the maximum force on the compression rate is non-monotoni...
Maximum-Entropy Inference with a Programmable Annealer
Chancellor, Nicholas; Vinci, Walter; Aeppli, Gabriel; Warburton, Paul A
2015-01-01
Optimisation problems in science and engineering typically involve finding the ground state (i.e. the minimum energy configuration) of a cost function with respect to many variables. If the variables are corrupted by noise then this approach maximises the likelihood that the solution found is correct. An alternative approach is to make use of prior statistical information about the noise in conjunction with Bayes's theorem. The maximum entropy solution to the problem then takes the form of a Boltzmann distribution over the ground and excited states of the cost function. Here we use a programmable Josephson junction array for the information decoding problem which we simulate as a random Ising model in a field. We show experimentally that maximum entropy decoding at finite temperature can in certain cases give competitive and even slightly better bit-error-rates than the maximum likelihood approach at zero temperature, confirming that useful information can be extracted from the excited states of the annealing...
Thermally favourable gauge mediation
Dalianis, Ioannis, E-mail: Ioannis.Dalianis@fuw.edu.p [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ul. Hoza 69, Warsaw (Poland); Lalak, Zygmunt, E-mail: Zygmunt.Lalak@fuw.edu.p [Institute of Theoretical Physics, Faculty of Physics, University of Warsaw, ul. Hoza 69, Warsaw (Poland)
2011-03-14
We discuss the thermal evolution of the spurion and messenger fields of ordinary gauge mediation models taking into account the Standard Model degrees of freedom. It is shown that for thermalized messengers the metastable susy breaking vacuum becomes thermally selected provided that the susy breaking sector is sufficiently weakly coupled to messengers or to any other observable field.
Thermal Performance Benchmarking (Presentation)
Moreno, G.
2014-11-01
This project will benchmark the thermal characteristics of automotive power electronics and electric motor thermal management systems. Recent vehicle systems will be benchmarked to establish baseline metrics, evaluate advantages and disadvantages of different thermal management systems, and identify areas of improvement to advance the state-of-the-art.
Electric Motor Thermal Management
Bennion, Kevin S [National Renewable Energy Laboratory (NREL), Golden, CO (United States)
2017-09-01
Thermal management enables more efficient and cost-effective motors. This Annual Merit Review presentation describes the technical accomplishments and progress in electric motor thermal management R&D over the last year. This project supports a broad industry demand for data, analysis methods, and experimental techniques to improve and better understand motor thermal management.
2003-01-15
171.64.49.29. Redistribution subject toneed high thermal conductivity. In others, such as thermal barriers or thermoelectric materials used for solid-state re... thermal barriers . Significant decreases in conductivity have been observed recently in nanocrystalline ZrO2 :Y2O3 ~Ref. 118! and attributed to the
Estimating the maximum potential revenue for grid connected electricity storage :
Byrne, Raymond Harry; Silva Monroy, Cesar Augusto.
2012-12-01
The valuation of an electricity storage device is based on the expected future cash flow generated by the device. Two potential sources of income for an electricity storage system are energy arbitrage and participation in the frequency regulation market. Energy arbitrage refers to purchasing (stor- ing) energy when electricity prices are low, and selling (discharging) energy when electricity prices are high. Frequency regulation is an ancillary service geared towards maintaining system frequency, and is typically procured by the independent system operator in some type of market. This paper outlines the calculations required to estimate the maximum potential revenue from participating in these two activities. First, a mathematical model is presented for the state of charge as a function of the storage device parameters and the quantities of electricity purchased/sold as well as the quantities o ered into the regulation market. Using this mathematical model, we present a linear programming optimization approach to calculating the maximum potential revenue from an elec- tricity storage device. The calculation of the maximum potential revenue is critical in developing an upper bound on the value of storage, as a benchmark for evaluating potential trading strate- gies, and a tool for capital nance risk assessment. Then, we use historical California Independent System Operator (CAISO) data from 2010-2011 to evaluate the maximum potential revenue from the Tehachapi wind energy storage project, an American Recovery and Reinvestment Act of 2009 (ARRA) energy storage demonstration project. We investigate the maximum potential revenue from two di erent scenarios: arbitrage only and arbitrage combined with the regulation market. Our analysis shows that participation in the regulation market produces four times the revenue compared to arbitrage in the CAISO market using 2010 and 2011 data. Then we evaluate several trading strategies to illustrate how they compare to the
Spatio-temporal observations of tertiary ozone maximum
V. F. Sofieva
2009-03-01
Full Text Available We present spatio-temporal distributions of tertiary ozone maximum (TOM, based on GOMOS (Global Ozone Monitoring by Occultation of Stars ozone measurements in 2002–2006. The tertiary ozone maximum is typically observed in the high-latitude winter mesosphere at altitude ~72 km. Although the explanation for this phenomenon has been found recently – low concentrations of odd-hydrogen cause the subsequent decrease in odd-oxygen losses – models have had significant deviations from existing observations until recently. Good coverage of polar night regions by GOMOS data has allowed for the first time obtaining spatial and temporal observational distributions of night-time ozone mixing ratio in the mesosphere.
The distributions obtained from GOMOS data have specific features, which are variable from year to year. In particular, due to a long lifetime of ozone in polar night conditions, the downward transport of polar air by the meridional circulation is clearly observed in the tertiary ozone maximum time series. Although the maximum tertiary ozone mixing ratio is achieved close to the polar night terminator (as predicted by the theory, TOM can be observed also at very high latitudes, not only in the beginning and at the end, but also in the middle of winter. We have compared the observational spatio-temporal distributions of tertiary ozone maximum with that obtained using WACCM (Whole Atmosphere Community Climate Model and found that the specific features are reproduced satisfactorily by the model.
Since ozone in the mesosphere is very sensitive to HO_{x} concentrations, energetic particle precipitation can significantly modify the shape of the ozone profiles. In particular, GOMOS observations have shown that the tertiary ozone maximum was temporarily destroyed during the January 2005 and December 2006 solar proton events as a result of the HO_{x} enhancement from the increased ionization.
Beat the Deviations in Estimating Maximum Power of Thermoelectric Modules
Gao, Junling; Chen, Min
2013-01-01
Under a certain temperature difference, the maximum power of a thermoelectric module can be estimated by the open-circuit voltage and the short-circuit current. In practical measurement, there exist two switch modes, either from open to short or from short to open, but the two modes can give...... different estimations on the maximum power. Using TEG-127-2.8-3.5-250 and TEG-127-1.4-1.6-250 as two examples, the difference is about 10%, leading to some deviations with the temperature change. This paper analyzes such differences by means of a nonlinear numerical model of thermoelectricity, and finds out...
Microcanonical origin of the maximum entropy principle for open systems.
Lee, Julian; Pressé, Steve
2012-10-01
There are two distinct approaches for deriving the canonical ensemble. The canonical ensemble either follows as a special limit of the microcanonical ensemble or alternatively follows from the maximum entropy principle. We show the equivalence of these two approaches by applying the maximum entropy formulation to a closed universe consisting of an open system plus bath. We show that the target function for deriving the canonical distribution emerges as a natural consequence of partial maximization of the entropy over the bath degrees of freedom alone. By extending this mathematical formalism to dynamical paths rather than equilibrium ensembles, the result provides an alternative justification for the principle of path entropy maximization as well.
Information Entropy Production of Spatio-Temporal Maximum Entropy Distributions
Cofre, Rodrigo
2015-01-01
Spiking activity from populations of neurons display causal interactions and memory effects. Therefore, they are expected to show some degree of irreversibility in time. Motivated by the spike train statistics, in this paper we build a framework to quantify the degree of irreversibility of any maximum entropy distribution. Our approach is based on the transfer matrix technique, which enables us to find an homogeneous irreducible Markov chain that shares the same maximum entropy measure. We provide relevant examples in the context of spike train statistics
Semiparametric maximum likelihood for nonlinear regression with measurement errors.
Suh, Eun-Young; Schafer, Daniel W
2002-06-01
This article demonstrates semiparametric maximum likelihood estimation of a nonlinear growth model for fish lengths using imprecisely measured ages. Data on the species corvina reina, found in the Gulf of Nicoya, Costa Rica, consist of lengths and imprecise ages for 168 fish and precise ages for a subset of 16 fish. The statistical problem may therefore be classified as nonlinear errors-in-variables regression with internal validation data. Inferential techniques are based on ideas extracted from several previous works on semiparametric maximum likelihood for errors-in-variables problems. The illustration of the example clarifies practical aspects of the associated computational, inferential, and data analytic techniques.
Maximum length scale in density based topology optimization
Lazarov, Boyan Stefanov; Wang, Fengwen
2017-01-01
The focus of this work is on two new techniques for imposing maximum length scale in topology optimization. Restrictions on the maximum length scale provide designers with full control over the optimized structure and open possibilities to tailor the optimized design for broader range...... of manufacturing processes by fulfilling the associated technological constraints. One of the proposed methods is based on combination of several filters and builds on top of the classical density filtering which can be viewed as a low pass filter applied to the design parametrization. The main idea...
On the Effect of Mortgages of Maximum Amount
YangZongping
2005-01-01
Since the enactment of the PRC Guarantee Law, mortgages of maximum amount has won wide application in a variety of business occupations and particularly in banking. Compared with the rich content of the 21clause statute on mortgages of maximum amount in Japan's Civil Law, the Chinese law has only four principled clauses. Its lack of operability plus its legislative gaps and defects has a severe impact on the positive effectiveness of the law. The core issue is the question of effectiveness. Because the principles stipulated in the Law run counter to the diversity of its actual practices,
A Maximum Entropy Method for a Robust Portfolio Problem
Yingying Xu
2014-06-01
Full Text Available We propose a continuous maximum entropy method to investigate the robustoptimal portfolio selection problem for the market with transaction costs and dividends.This robust model aims to maximize the worst-case portfolio return in the case that allof asset returns lie within some prescribed intervals. A numerical optimal solution tothe problem is obtained by using a continuous maximum entropy method. Furthermore,some numerical experiments indicate that the robust model in this paper can result in betterportfolio performance than a classical mean-variance model.
On the maximum grain size entrained by photoevaporative winds
Hutchison, Mark A; Maddison, Sarah T
2016-01-01
We model the behaviour of dust grains entrained by photoevaporation-driven winds from protoplanetary discs assuming a non-rotating, plane-parallel disc. We obtain an analytic expression for the maximum entrainable grain size in extreme-UV radiation-driven winds, which we demonstrate to be proportional to the mass loss rate of the disc. When compared with our hydrodynamic simulations, the model reproduces almost all of the wind properties for the gas and dust. In typical turbulent discs, the entrained grain sizes in the wind are smaller than the theoretical maximum everywhere but the inner disc due to dust settling.
Modified maximum likelihood registration based on information fusion
Yongqing Qi; Zhongliang Jing; Shiqiang Hu
2007-01-01
The bias estimation of passive sensors is considered based on information fusion in multi-platform multisensor tracking system. The unobservable problem of bearing-only tracking in blind spot is analyzed. A modified maximum likelihood method, which uses the redundant information of multi-sensor system to calculate the target position, is investigated to estimate the biases. Monte Carlo simulation results show that the modified method eliminates the effect of unobservable problem in the blind spot and can estimate the biases more rapidly and accurately than maximum likelihood method. It is statistically efficient since the standard deviation of bias estimation errors meets the theoretical lower bounds.
Maximum-entropy distributions of correlated variables with prespecified marginals.
Larralde, Hernán
2012-12-01
The problem of determining the joint probability distributions for correlated random variables with prespecified marginals is considered. When the joint distribution satisfying all the required conditions is not unique, the "most unbiased" choice corresponds to the distribution of maximum entropy. The calculation of the maximum-entropy distribution requires the solution of rather complicated nonlinear coupled integral equations, exact solutions to which are obtained for the case of Gaussian marginals; otherwise, the solution can be expressed as a perturbation around the product of the marginals if the marginal moments exist.
A discussion on maximum entropy production and information theory
Bruers, Stijn [Instituut voor Theoretische Fysica, Celestijnenlaan 200D, Katholieke Universiteit Leuven, B-3001 Leuven (Belgium)
2007-07-06
We will discuss the maximum entropy production (MaxEP) principle based on Jaynes' information theoretical arguments, as was done by Dewar (2003 J. Phys. A: Math. Gen. 36 631-41, 2005 J. Phys. A: Math. Gen. 38 371-81). With the help of a simple mathematical model of a non-equilibrium system, we will show how to derive minimum and maximum entropy production. Furthermore, the model will help us to clarify some confusing points and to see differences between some MaxEP studies in the literature.
Generalized Relativistic Wave Equations with Intrinsic Maximum Momentum
Ching, Chee Leong
2013-01-01
We examine the nonperturbative effect of maximum momentum on the relativistic wave equations. In momentum representation, we obtain the exact eigen-energies and wavefunctions of one-dimensional Klein-Gordon and Dirac equation with linear confining potentials, and the Dirac oscillator. Bound state solutions are only possible when the strength of scalar potential are stronger than vector potential. The energy spectrum of the systems studied are bounded from above, whereby classical characteristics are observed in the uncertainties of position and momentum operators. Also, there is a truncation in the maximum number of bound states that is allowed. Some of these quantum-gravitational features may have future applications.
Generalized relativistic wave equations with intrinsic maximum momentum
Ching, Chee Leong; Ng, Wei Khim
2014-05-01
We examine the nonperturbative effect of maximum momentum on the relativistic wave equations. In momentum representation, we obtain the exact eigen-energies and wave functions of one-dimensional Klein-Gordon and Dirac equation with linear confining potentials, and the Dirac oscillator. Bound state solutions are only possible when the strength of scalar potential is stronger than vector potential. The energy spectrum of the systems studied is bounded from above, whereby classical characteristics are observed in the uncertainties of position and momentum operators. Also, there is a truncation in the maximum number of bound states that is allowed. Some of these quantum-gravitational features may have future applications.
Parameter estimation in X-ray astronomy using maximum likelihood
Wachter, K.; Leach, R.; Kellogg, E.
1979-01-01
Methods of estimation of parameter values and confidence regions by maximum likelihood and Fisher efficient scores starting from Poisson probabilities are developed for the nonlinear spectral functions commonly encountered in X-ray astronomy. It is argued that these methods offer significant advantages over the commonly used alternatives called minimum chi-squared because they rely on less pervasive statistical approximations and so may be expected to remain valid for data of poorer quality. Extensive numerical simulations of the maximum likelihood method are reported which verify that the best-fit parameter value and confidence region calculations are correct over a wide range of input spectra.
A maximum in the strength of nanocrystalline copper
Schiøtz, Jakob; Jacobsen, Karsten Wedel
2003-01-01
We used molecular dynamics simulations with system sizes up to 100 million atoms to simulate plastic deformation of nanocrystalline copper. By varying the grain size between 5 and 50 nanometers, we show that the flow stress and thus the strength exhibit a maximum at a grain size of 10 to 15...... nanometers. This maximum is because of a shift in the microscopic deformation mechanism from dislocation-mediated plasticity in the coarse-grained material to grain boundary sliding in the nanocrystalline region. The simulations allow us to observe the mechanisms behind the grain-size dependence...
Efficiency of autonomous soft nanomachines at maximum power.
Seifert, Udo
2011-01-14
We consider nanosized artificial or biological machines working in steady state enforced by imposing nonequilibrium concentrations of solutes or by applying external forces, torques, or electric fields. For unicyclic and strongly coupled multicyclic machines, efficiency at maximum power is not bounded by the linear response value 1/2. For strong driving, it can even approach the thermodynamic limit 1. Quite generally, such machines fall into three different classes characterized, respectively, as "strong and efficient," "strong and inefficient," and "balanced." For weakly coupled multicyclic machines, efficiency at maximum power has lost any universality even in the linear response regime.
Evidence for enhanced thermal conduction through percolating structures in nanofluids
Philip, John; Shima, P D; Raj, Baldev [Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India)], E-mail: philip@igcar.gov.in
2008-07-30
The unusually large enhancement of thermal conductivity (k/k{sub f}{approx}4.0, where k and k{sub f} are the thermal conductivities of the nanofluid and the base fluid, respectively) observed in a nanofluid containing linear chain-like aggregates provides direct evidence for efficient transport of heat through percolating paths. The nanofluid used was a stable colloidal suspension of magnetite (Fe{sub 3}O{sub 4}) nanoparticles of average diameter 6.7 nm, coated with oleic acid and dispersed in kerosene. The maximum enhancement under magnetic field was about 48{phi} (where {phi} is the volume fraction). The maximum enhancement is observed when chain-like aggregates are uniformly dispersed without clumping. These results also suggest that nanofluids containing well-dispersed nanoparticles (without aggregates) do not exhibit significant enhancement of thermal conductivity. Our findings offer promising applications for developing a new generation of nanofluids with tunable thermal conductivity.
Evidence for enhanced thermal conduction through percolating structures in nanofluids.
Philip, John; Shima, P D; Raj, Baldev
2008-07-30
The unusually large enhancement of thermal conductivity (k/k(f)∼4.0, where k and k(f) are the thermal conductivities of the nanofluid and the base fluid, respectively) observed in a nanofluid containing linear chain-like aggregates provides direct evidence for efficient transport of heat through percolating paths. The nanofluid used was a stable colloidal suspension of magnetite (Fe(3)O(4)) nanoparticles of average diameter 6.7 nm, coated with oleic acid and dispersed in kerosene. The maximum enhancement under magnetic field was about 48φ (where φ is the volume fraction). The maximum enhancement is observed when chain-like aggregates are uniformly dispersed without clumping. These results also suggest that nanofluids containing well-dispersed nanoparticles (without aggregates) do not exhibit significant enhancement of thermal conductivity. Our findings offer promising applications for developing a new generation of nanofluids with tunable thermal conductivity.
Thermal Radiative Properties of Xonotlite Insulation Material
Xinxin ZHANG; Gaosheng WEI; Fan YU
2005-01-01
This paper presents experimental results of thermal radiative properties of xonotlite-type calcium silicate insulation material. Transmittance spectra were first taken using Fourier transform infrared spectrometer (FTIR)for the samples with ρ = 234 kg/m3. Specific extinction coefficient spectra were then obtained by applying Beer's law.Finally,by using the diffusion approximation,the specific Rossland mean extinction coefficients and radiative thermal conductivities were obtained for various temperatures. The results show that the specific spectral extinction coefficient of xonotlite is larger than 7 m2/kg in the whole measured spectra, and diffusion approximation equation is a reasonable description of radiative heat transfer in xonotlite insulation material. The specific Rossland mean extinction coefficient of xonotlite has a maximum ualue at 400 K and the radiative thermal conductivity is almost proportional to the cube of temperature.
Specific heat and thermal conductivity of nanomaterials
Bhatt, Sandhya; Kumar, Raghuvesh; Kumar, Munish
2017-01-01
A model is proposed to study the size and shape effects on specific heat and thermal conductivity of nanomaterials. The formulation developed for specific heat is based on the basic concept of cohesive energy and melting temperature. The specific heat of Ag and Au nanoparticles is reported and the effect of size and shape has been studied. We observed that specific heat increases with the reduction of particle size having maximum shape effect for spherical nanoparticle. To provide a more critical test, we extended our model to study the thermal conductivity and used it for the study of Si, diamond, Cu, Ni, Ar, ZrO2, BaTiO3 and SrTiO3 nanomaterials. A significant reduction is found in the thermal conductivity for nanomaterials by decreasing the size. The model predictions are consistent with the available experimental and simulation results. This demonstrates the suitability of the model proposed in this paper.
Necessity of Eigenstate Thermalization
De Palma, Giacomo; Serafini, Alessio; Giovannetti, Vittorio; Cramer, Marcus
2015-11-01
Under the eigenstate thermalization hypothesis (ETH), quantum-quenched systems equilibrate towards canonical, thermal ensembles. While at first glance the ETH might seem a very strong hypothesis, we show that it is indeed not only sufficient but also necessary for thermalization. More specifically, we consider systems coupled to baths with well-defined macroscopic temperature and show that whenever all product states thermalize then the ETH must hold. Our result definitively settles the question of determining whether a quantum system has a thermal behavior, reducing it to checking whether its Hamiltonian satisfies the ETH.
A PC- Based Transient Method for Thermal Conductivity Measurement.
A.K. Singh
2000-10-01
Full Text Available In this paper, an indigenously developed thermal probe has been interfaced with a PC for automated measurement of thermal conductivity (K . The developed system has been calibrated and standardised by measuring K of glycerol. The maximum percentage error, for repeated sets of observations, was within 7.29 per cent of standard value reported for glycerol. This methodology has been successfully employed for measuring K of propellant oxidisers, additives, binders, etc.
A maximum-entropy approach to the adiabatic freezing of a supercooled liquid.
Prestipino, Santi
2013-04-28
I employ the van der Waals theory of Baus and co-workers to analyze the fast, adiabatic decay of a supercooled liquid in a closed vessel with which the solidification process usually starts. By imposing a further constraint on either the system volume or pressure, I use the maximum-entropy method to quantify the fraction of liquid that is transformed into solid as a function of undercooling and of the amount of a foreign gas that could possibly be also present in the test tube. Upon looking at the implications of thermal and mechanical insulation for the energy cost of forming a solid droplet within the liquid, I identify one situation where the onset of solidification inevitably occurs near the wall in contact with the bath.
Temperature dependence of attitude sensor coalignments on the Solar Maximum Mission (SMM)
Pitone, D. S.; Eudell, A. H.; Patt, F. S.
1990-01-01
The temperature correlation of the relative coalignment between the fine-pointing sun sensor and fixed-head star trackers measured on the Solar Maximum Mission (SMM) is analyzed. An overview of the SMM, including mission history and configuration, is given. Possible causes of the misalignment variation are discussed, with focus placed on spacecraft bending due to solar-radiation pressure, electronic or mechanical changes in the sensors, uncertainty in the attitude solutions, and mounting-plate expansion and contraction due to thermal effects. Yaw misalignment variation from the temperature profile is assessed, and suggestions for spacecraft operations are presented, involving methods to incorporate flight measurements of the temperature-versus-alignment function and its variance in operational procedures and the spacecraft structure temperatures in the attitude telemetry record.
Efficiency at maximum power of a quantum heat engine based on two coupled oscillators.
Wang, Jianhui; Ye, Zhuolin; Lai, Yiming; Li, Weisheng; He, Jizhou
2015-06-01
We propose and theoretically investigate a system of two coupled harmonic oscillators as a heat engine. We show how these two coupled oscillators within undamped regime can be controlled to realize an Otto cycle that consists of two adiabatic and two isochoric processes. During the two isochores the harmonic system is embedded in two heat reservoirs at constant temperatures T(h) and T(c)(semigroup approach to model the thermal relaxation dynamics along the two isochoric processes, and we find the upper bound of efficiency at maximum power (EMP) η* to be a function of the Carnot efficiency η(C)(=1-T(c)/T(h)): η*≤η(+)≡η(C)(2)/[η(C)-(1-η(C))ln(1-η(C))], identical to those previously derived from ideal (noninteracting) microscopic, mesoscopic, and macroscopic systems.
Maximum acceptable inherent buoyancy limit for aircrew/passenger helicopter immersion suit systems.
Brooks, C J
1988-12-01
Helicopter crew and passengers flying over cold water wear immersion suits to provide hypothermic protection in case of ditching in cold water. The suits and linings have trapped air in the material to provide the necessary insulation and are thus very buoyant. By paradox, this buoyancy may be too much for a survivor to overcome in escaping from the cabin of a rapidly sinking inverted helicopter. The Canadian General Standard Board requested that research be conducted to investigate what should be the maximum inherent buoyancy in an immersion suit that would not inhibit escape, yet would provide adequate thermal insulation. This experiment reports on 12 subjects who safely escaped with 146N (33 lbf) of added buoyancy from a helicopter underwater escape trainer. It discusses the logic for and recommendation that the inherent buoyancy in a helicopter crew/passenger immersion suit system should not exceed this figure.
Kernel principal component and maximum autocorrelation factor analyses for change detection
Nielsen, Allan Aasbjerg; Canty, Morton John
2009-01-01
in Nevada acquired on successive passes of the Landsat-5 satellite in August-September 1991. The six-band images (the thermal band is omitted) with 1,000 by 1,000 28.5 m pixels were first processed with the iteratively re-weighted MAD (IR-MAD) algorithm in order to discriminate change. Then the MAD image......Principal component analysis (PCA) has often been used to detect change over time in remotely sensed images. A commonly used technique consists of finding the projections along the eigenvectors for data consisting of pair-wise (perhaps generalized) differences between corresponding spectral bands...... covering the same geographical region acquired at two different time points. In this paper kernel versions of the principal component and maximum autocorrelation factor (MAF) transformations are used to carry out the analysis. An example is based on bi-temporal Landsat-5 TM imagery over irrigation fields...
Thermal Management and Thermal Protection Systems
Hasnain, Aqib
2016-01-01
During my internship in the Thermal Design Branch (ES3), I contributed to two main projects: i) novel passive thermal management system for future human exploration, ii) AVCOAT undercut thermal analysis. i) As NASA prepares to further expand human and robotic presence in space, it is well known that spacecraft architectures will be challenged with unprecedented thermal environments. Future exploration activities will have the need of thermal management systems that can provide higher reliability, mass and power reduction and increased performance. In an effort to start addressing the current technical gaps the NASA Johnson Space Center Passive Thermal Discipline has engaged in technology development activities. One of these activities was done through an in-house Passive Thermal Management System (PTMS) design for a lunar lander. The proposed PTMS, functional in both microgravity and gravity environments, consists of three main components: a heat spreader, a novel hybrid wick Variable Conductance Heat Pipe (VCHP), and a radiator. The aim of this PTMS is to keep electronics on a vehicle within their temperature limits (0 and 50 C for the current design) during all mission phases including multiple lunar day/night cycles. The VCHP was tested to verify its thermal performance. I created a thermal math model using Thermal Desktop (TD) and analyzed it to predict the PTMS performance. After testing, the test data provided a means to correlate the thermal math model. This correlation took into account conduction and convection heat transfer, representing the actual benchtop test. Since this PTMS is proposed for space missions, a vacuum test will be taking place to provide confidence that the system is functional in space environments. Therefore, the model was modified to include a vacuum chamber with a liquid nitrogen shroud while taking into account conduction and radiation heat transfer. Infrared Lamps were modelled and introduced into the model to simulate the sun
A Brooks type theorem for the maximum local edge connectivity
Stiebitz, Michael; Toft, Bjarne
2017-01-01
For a graph $G$, let $\\cn(G)$ and $\\la(G)$ denote the chromatic number of $G$ and the maximum local edge connectivity of $G$, respectively. A result of Dirac \\cite{Dirac53} implies that every graph $G$ satisfies $\\cn(G)\\leq \\la(G)+1$. In this paper we characterize the graphs $G$ for which $\\cn(G)...
Prediction of Maximum Oxygen Consumption from Walking, Jogging, or Running.
Larsen, Gary E.; George, James D.; Alexander, Jeffrey L.; Fellingham, Gilbert W.; Aldana, Steve G.; Parcell, Allen C.
2002-01-01
Developed a cardiorespiratory endurance test that retained the inherent advantages of submaximal testing while eliminating reliance on heart rate measurement in predicting maximum oxygen uptake (VO2max). College students completed three exercise tests. The 1.5-mile endurance test predicted VO2max from submaximal exercise without requiring heart…
On the maximum backscattering cross section of passive linear arrays
Solymar, L.; Appel-Hansen, Jørgen
1974-01-01
The maximum backscattering cross section of an equispaced linear array connected to a reactive network and consisting of isotropic radiators is calculated forn = 2, 3, and 4 elements as a function of the incident angle and of the distance between the elements. On the basis of the results obtained...
Scientific substantination of maximum allowable concentration of fluopicolide in water
Pelo I.М.
2014-03-01
Full Text Available In order to substantiate fluopicolide maximum allowable concentration in the water of water reservoirs the research was carried out. Methods of study: laboratory hygienic experiment using organoleptic and sanitary-chemical, sanitary-toxicological, sanitary-microbiological and mathematical methods. The results of fluopicolide influence on organoleptic properties of water, sanitary regimen of reservoirs for household purposes were given and its subthreshold concentration in water by sanitary and toxicological hazard index was calculated. The threshold concentration of the substance by the main hazard criteria was established, the maximum allowable concentration in water was substantiated. The studies led to the following conclusions: fluopicolide threshold concentration in water by organoleptic hazard index (limiting criterion – the smell – 0.15 mg/dm3, general sanitary hazard index (limiting criteria – impact on the number of saprophytic microflora, biochemical oxygen demand and nitrification – 0.015 mg/dm3, the maximum noneffective concentration – 0.14 mg/dm3, the maximum allowable concentration - 0.015 mg/dm3.
Effects of bruxism on the maximum bite force
Todić Jelena T.
2017-01-01
Full Text Available Background/Aim. Bruxism is a parafunctional activity of the masticatory system, which is characterized by clenching or grinding of teeth. The purpose of this study was to determine whether the presence of bruxism has impact on maximum bite force, with particular reference to the potential impact of gender on bite force values. Methods. This study included two groups of subjects: without and with bruxism. The presence of bruxism in the subjects was registered using a specific clinical questionnaire on bruxism and physical examination. The subjects from both groups were submitted to the procedure of measuring the maximum bite pressure and occlusal contact area using a single-sheet pressure-sensitive films (Fuji Prescale MS and HS Film. Maximal bite force was obtained by multiplying maximal bite pressure and occlusal contact area values. Results. The average values of maximal bite force were significantly higher in the subjects with bruxism compared to those without bruxism (p 0.01. Maximal bite force was significantly higher in the males compared to the females in all segments of the research. Conclusion. The presence of bruxism influences the increase in the maximum bite force as shown in this study. Gender is a significant determinant of bite force. Registration of maximum bite force can be used in diagnosing and analysing pathophysiological events during bruxism.
A Unified Maximum Likelihood Approach to Document Retrieval.
Bodoff, David; Enache, Daniel; Kambil, Ajit; Simon, Gary; Yukhimets, Alex
2001-01-01
Addresses the query- versus document-oriented dichotomy in information retrieval. Introduces a maximum likelihood approach to utilizing feedback data that can be used to construct a concrete object function that estimates both document and query parameters in accordance with all available feedback data. (AEF)
Sequential and Parallel Algorithms for Finding a Maximum Convex Polygon
Fischer, Paul
1997-01-01
such a polygon which is maximal with respect to area can be found in time O(n³ log n). With the same running time one can also find such a polygon which contains a maximum number of positive points. If, in addition, the number of vertices of the polygon is restricted to be at most M, then the running time...
Prediction of Maximum Oxygen Consumption from Walking, Jogging, or Running.
Larsen, Gary E.; George, James D.; Alexander, Jeffrey L.; Fellingham, Gilbert W.; Aldana, Steve G.; Parcell, Allen C.
2002-01-01
Developed a cardiorespiratory endurance test that retained the inherent advantages of submaximal testing while eliminating reliance on heart rate measurement in predicting maximum oxygen uptake (VO2max). College students completed three exercise tests. The 1.5-mile endurance test predicted VO2max from submaximal exercise without requiring heart…
34 CFR 682.204 - Maximum loan amounts.
2010-07-01
... 34 Education 3 2010-07-01 2010-07-01 false Maximum loan amounts. 682.204 Section 682.204 Education Regulations of the Offices of the Department of Education (Continued) OFFICE OF POSTSECONDARY EDUCATION, DEPARTMENT OF EDUCATION FEDERAL FAMILY EDUCATION LOAN (FFEL) PROGRAM General Provisions § 682.204...
Triadic conceptual structure of the maximum entropy approach to evolution.
Herrmann-Pillath, Carsten; Salthe, Stanley N
2011-03-01
Many problems in evolutionary theory are cast in dyadic terms, such as the polar oppositions of organism and environment. We argue that a triadic conceptual structure offers an alternative perspective under which the information generating role of evolution as a physical process can be analyzed, and propose a new diagrammatic approach. Peirce's natural philosophy was deeply influenced by his reception of both Darwin's theory and thermodynamics. Thus, we elaborate on a new synthesis which puts together his theory of signs and modern Maximum Entropy approaches to evolution in a process discourse. Following recent contributions to the naturalization of Peircean semiosis, pointing towards 'physiosemiosis' or 'pansemiosis', we show that triadic structures involve the conjunction of three different kinds of causality, efficient, formal and final. In this, we accommodate the state-centered thermodynamic framework to a process approach. We apply this on Ulanowicz's analysis of autocatalytic cycles as primordial patterns of life. This paves the way for a semiotic view of thermodynamics which is built on the idea that Peircean interpretants are systems of physical inference devices evolving under natural selection. In this view, the principles of Maximum Entropy, Maximum Power, and Maximum Entropy Production work together to drive the emergence of information carrying structures, which at the same time maximize information capacity as well as the gradients of energy flows, such that ultimately, contrary to Schrödinger's seminal contribution, the evolutionary process is seen to be a physical expression of the Second Law.
Maximum-entropy probability distributions under Lp-norm constraints
Dolinar, S.
1991-01-01
Continuous probability density functions and discrete probability mass functions are tabulated which maximize the differential entropy or absolute entropy, respectively, among all probability distributions with a given L sub p norm (i.e., a given pth absolute moment when p is a finite integer) and unconstrained or constrained value set. Expressions for the maximum entropy are evaluated as functions of the L sub p norm. The most interesting results are obtained and plotted for unconstrained (real valued) continuous random variables and for integer valued discrete random variables. The maximum entropy expressions are obtained in closed form for unconstrained continuous random variables, and in this case there is a simple straight line relationship between the maximum differential entropy and the logarithm of the L sub p norm. Corresponding expressions for arbitrary discrete and constrained continuous random variables are given parametrically; closed form expressions are available only for special cases. However, simpler alternative bounds on the maximum entropy of integer valued discrete random variables are obtained by applying the differential entropy results to continuous random variables which approximate the integer valued random variables in a natural manner. All the results are presented in an integrated framework that includes continuous and discrete random variables, constraints on the permissible value set, and all possible values of p. Understanding such as this is useful in evaluating the performance of data compression schemes.
Exploiting the Maximum Entropy Principle to Increase Retrieval Effectiveness.
Cooper, William S.
1983-01-01
Presents information retrieval design approach in which queries of computer-based system consist of sets of terms, either unweighted or weighted with subjective term precision estimates, and retrieval outputs ranked by probability of usefulness estimated by "maximum entropy principle." Boolean and weighted request systems are discussed.…
The constraint rule of the maximum entropy principle
Uffink, J.
2001-01-01
The principle of maximum entropy is a method for assigning values to probability distributions on the basis of partial information. In usual formulations of this and related methods of inference one assumes that this partial information takes the form of a constraint on allowed probability distribut
On the maximum entropy principle in non-extensive thermostatistics
Naudts, Jan
2004-01-01
It is possible to derive the maximum entropy principle from thermodynamic stability requirements. Using as a starting point the equilibrium probability distribution, currently used in non-extensive thermostatistics, it turns out that the relevant entropy function is Renyi's alpha-entropy, and not Tsallis' entropy.
MAXIMUM-LIKELIHOOD-ESTIMATION OF THE ENTROPY OF AN ATTRACTOR
SCHOUTEN, JC; TAKENS, F; VANDENBLEEK, CM
1994-01-01
In this paper, a maximum-likelihood estimate of the (Kolmogorov) entropy of an attractor is proposed that can be obtained directly from a time series. Also, the relative standard deviation of the entropy estimate is derived; it is dependent on the entropy and on the number of samples used in the est
Maximum-Entropy Inference with a Programmable Annealer.
Chancellor, Nicholas; Szoke, Szilard; Vinci, Walter; Aeppli, Gabriel; Warburton, Paul A
2016-03-03
Optimisation problems typically involve finding the ground state (i.e. the minimum energy configuration) of a cost function with respect to many variables. If the variables are corrupted by noise then this maximises the likelihood that the solution is correct. The maximum entropy solution on the other hand takes the form of a Boltzmann distribution over the ground and excited states of the cost function to correct for noise. Here we use a programmable annealer for the information decoding problem which we simulate as a random Ising model in a field. We show experimentally that finite temperature maximum entropy decoding can give slightly better bit-error-rates than the maximum likelihood approach, confirming that useful information can be extracted from the excited states of the annealer. Furthermore we introduce a bit-by-bit analytical method which is agnostic to the specific application and use it to show that the annealer samples from a highly Boltzmann-like distribution. Machines of this kind are therefore candidates for use in a variety of machine learning applications which exploit maximum entropy inference, including language processing and image recognition.
40 CFR 35.145 - Maximum federal share.
2010-07-01
... STATE AND LOCAL ASSISTANCE Environmental Program Grants Air Pollution Control (section 105) § 35.145 Maximum federal share. (a) The Regional Administrator may provide air pollution control agencies, as... programs for the prevention and control of air pollution or implementing national primary and...
Maximum Safety Regenerative Power Tracking for DC Traction Power Systems
Guifu Du
2017-02-01
Full Text Available Direct current (DC traction power systems are widely used in metro transport systems, with running rails usually being used as return conductors. When traction current flows through the running rails, a potential voltage known as “rail potential” is generated between the rails and ground. Currently, abnormal rises of rail potential exist in many railway lines during the operation of railway systems. Excessively high rail potentials pose a threat to human life and to devices connected to the rails. In this paper, the effect of regenerative power distribution on rail potential is analyzed. Maximum safety regenerative power tracking is proposed for the control of maximum absolute rail potential and energy consumption during the operation of DC traction power systems. The dwell time of multiple trains at each station and the trigger voltage of the regenerative energy absorbing device (READ are optimized based on an improved particle swarm optimization (PSO algorithm to manage the distribution of regenerative power. In this way, the maximum absolute rail potential and energy consumption of DC traction power systems can be reduced. The operation data of Guangzhou Metro Line 2 are used in the simulations, and the results show that the scheme can reduce the maximum absolute rail potential and energy consumption effectively and guarantee the safety in energy saving of DC traction power systems.
A MAXIMUM ENTROPY METHOD FOR CONSTRAINED SEMI-INFINITEPROGRAMMING PROBLEMS
ZHOU Guanglu; WANG Changyu; SHI Zhenjun; SUN Qingying
1999-01-01
This paper presents a new method, called the maximum entropy method,for solving semi-infinite programming problems, in which thesemi-infinite programming problem is approximated by one with a singleconstraint. The convergence properties for this method are discussed.Numerical examples are given to show the high effciency of thealgorithm.
Closed form maximum likelihood estimator of conditional random fields
Zhu, Zhemin; Hiemstra, Djoerd; Apers, Peter M.G.; Wombacher, Andreas
2013-01-01
Training Conditional Random Fields (CRFs) can be very slow for big data. In this paper, we present a new training method for CRFs called {\\em Empirical Training} which is motivated by the concept of co-occurrence rate. We show that the standard training (unregularized) can have many maximum likeliho
Heteroscedastic one-factor models and marginal maximum likelihood estimation
Hessen, D.J.; Dolan, C.V.
2009-01-01
In the present paper, a general class of heteroscedastic one-factor models is considered. In these models, the residual variances of the observed scores are explicitly modelled as parametric functions of the one-dimensional factor score. A marginal maximum likelihood procedure for parameter estimati
Estruturas silicosas na gramínea Panicum maximum
Pedro Fontana Junior
1957-05-01
Full Text Available The silica structure of the grass Panicum maximum were studied by electron and phase contrast microscopy. Several interesting kinds of silica formation (spiklets were found. The most ineresting structures ressembels the "Schaumstruktur" found by HELMCKE in diatoms. Another interesting structure was described in the "silica cells" and a detailed study of the mophology of some different kinds of spiklets was made.
Bias Correction for Alternating Iterative Maximum Likelihood Estimators
Gang YU; Wei GAO; Ningzhong SHI
2013-01-01
In this paper,we give a definition of the alternating iterative maximum likelihood estimator (AIMLE) which is a biased estimator.Furthermore we adjust the AIMLE to result in asymptotically unbiased and consistent estimators by using a bootstrap iterative bias correction method as in Kuk (1995).Two examples and simulation results reported illustrate the performance of the bias correction for AIMLE.
21 CFR 801.415 - Maximum acceptable level of ozone.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Maximum acceptable level of ozone. 801.415 Section... level of ozone. (a) Ozone is a toxic gas with no known useful medical application in specific, adjunctive, or preventive therapy. In order for ozone to be effective as a germicide, it must be present in...
The maximum number of minimal codewords in long codes
Alahmadi, A.; Aldred, R.E.L.; dela Cruz, R.;
2013-01-01
Upper bounds on the maximum number of minimal codewords in a binary code follow from the theory of matroids. Random coding provides lower bounds. In this paper, we compare these bounds with analogous bounds for the cycle code of graphs. This problem (in the graphic case) was considered in 1981...
A Monte Carlo Evaluation of Maximum Likelihood Multidimensional Scaling Methods
Bijmolt, T.H.A.; Wedel, M.
1996-01-01
We compare three alternative Maximum Likelihood Multidimensional Scaling methods for pairwise dissimilarity ratings, namely MULTISCALE, MAXSCAL, and PROSCAL in a Monte Carlo study.The three MLMDS methods recover the true con gurations very well.The recovery of the true dimensionality depends on the
Quantum-dot Carnot engine at maximum power.
Esposito, Massimiliano; Kawai, Ryoichi; Lindenberg, Katja; Van den Broeck, Christian
2010-04-01
We evaluate the efficiency at maximum power of a quantum-dot Carnot heat engine. The universal values of the coefficients at the linear and quadratic order in the temperature gradient are reproduced. Curzon-Ahlborn efficiency is recovered in the limit of weak dissipation.